Science in Christian Perspective

Explanation, Testability, and the Theory of Evolution Part I
T. H.. LEITH 
Department of Natural Science 
Atkinson College, York University 
Toronto, Ontario, Canada

From: JASA 32 (March1980): 13-17.

Introduction

Among scientists and analysts of science there is an almost-universal acceptance of the thesis that life has evolved over a lengthy span of geological time and that it continues to do so. A few heretics question this interpretation, arguing that the evidence supports at most intraspecies or intragenus development with the fossil record being best interpreted in non-evolutionary terms. Others, though they operate within the usual consensus, differ on the evolutionary sequences suggested by paleontological and contemporary laboratory or field information, This paper refers to each of these ideas only obliquely.

Our attention is turned instead toward a quite different sort of criticism, the sort that takes exception to the way evolution has often been explained and defended. Such censures exhibit considerable variety. Some question the propriety of treating Darwin's own explanatory scheme as scientific during the half-century immediately following its appearance; others find later, and even current, theory equally unscientific by various standards. Some believe that understanding in biology, and particu larly in the interpretation of its historical data, is different from the ways by which we comprehend the physical world and that it is wrong-headed to attempt to fit evolutionary explanations to forms appropriate only in the physical sciences. Others accept current theory as at least a fair sketch for explaining the factual material but deny that the theory' provides, or at least intends to provide predictions by which it can he tested.

This paper serves primarily as an examination of the explanatory structures employed by evolutionary theorists and as a general evaluation of the testability of their schemes. The limits of space place constraints on the breadth and depth of toy inquiry, but sufficient analysis should be provided to give reasonable warrant for my general conclusions. If they clarify the similarities and contrasts of theorizing in evolutionary work and in the physical sciences, and of the kinds of things which count as their evidential support, I will he satisfied. After all, must readers are not specialists when it comes to evolu tionary technicalities and non-specialists commonly have qualms about evolution, if they have qualms at all, not because they can question descriptions of (say) evolutionary sequences with any competence, hot because they find inadequacies in the evolutionary explanations and in the standards of evidence employed by advocates of the theory. Let me begin then by looking at explanation as understood among physical scientists both because it is widely considered the ideal and because it will provide a context for my later comparisons with biology' and evolution.

Explanation in Physical Science

In the physical sciences we explain experience when whatever we wish to understand is derived from laws and theories. These are themselves testable within experience. It is this testability throughout which separates physical science, and anything emulating it, from other attempts at explanation.

In one form, scientific explanation in physical science uses statements described as universal because they are corroborated by experiences which appear to indicate that conditions of a certain sort, whenever they occur, are invariably accompanied by conditions of another sort. One or more of such laws, together with a set of circumstances found to be present, are used in practice to deduce the presence of conditions which we wish to explain. Thus, from the gas law for example, together with a particular pressure which we know obtains, we may explain an observed volume. Similarly, from the laws of gravity and motion as well as from information about the planets we may deduce the law of planetary motion; here a more general law is used to explain one of more restricted application.

Sometimes, however, the covering laws or law won't be universal in form but instead express probabilities
found by experience as when we state that p/q cases of A are cases of B. If we know that something y is a case of A we may then conclude that, with a probability p/q, y is a case of B.

Physical science employs, as well, what we may call theoretical explanations. Here a theory is proposed as an aid in understanding a set of laws found by careful observation or experiment. The theory explains the phenomena which exhibit these regularities in terms of assumed laws governing the behavior of imagined entities and their activity and, by the use of interpretations of these, indicates how they are to be related to the phenomena. The theory is therefore used to give a coherent and systematic account of a variety of different phenomena or empirical laws while explaining why these apply only within certain limits.

Sometimes this may be done by treating the theory as a set of axioms, arid theorems derived from these, together with interpretive rules by which the theorems are identified with empirical data. However, this technique often proves to be exceedingly difficult so that some model is employed to give an intelligible interpretation of the theory. For example a familiar physical system, having elements with familiar properties which in turn exhibit relationships expressed in familiar empiri cal laws, may be used to give a suggested meaning to the entities of the theory and their activity. We must, of course, always be aware that these theoretical entities and processes actually involve ideas lying beyond the familiar, ideas often quite strange to the earlier modes of thought found in the model, but which gain credibility by their employment in predicting empirical laws previously undiscovered.

The essence of all this is that, though laws perform a sort of explanatory function of their own, so that they are useful standing alone, scientists seek greater understanding through explaining the laws in terms of more general laws or theories. Here there is a binding requirement. As the strength of our purported explanation depends upon the confidence which we can place in the covering laws or theory, and as that is a function of the degree of corroboration which they have achieved in the face of severe testing, we must take pains to keep our covering laws or theory both testable and tested.

It is here that many explanations which are unlike those of physical science fail grandly, for, when we turn from explanation to prediction, the laws or theories which they employ, not being falsifiable by experiment or observation, predict everything and nothing. This is because they cannot indicate what it is in experience that would be different were they untrue. Thus, for example, an explanation of the events of the world as due to the will of God will ordinarily have no prognostic utility; as a consequence the explanation is untestable and on that account would appear to many to be unworthy of rational belief. This result may be avoided if we somehow had a prior knowledge of God's will or if we believe the explanation because it follows from a broader set of beliefs which have their own justification. In the former case fulfilled prediction would provide the vehicle by which the explanation gains credibility while, in the latter, the explanation gains support in spite of its inability to anticipate events.

Is Explanation in Evolution Different?

It has been argued that evolutionary explications are rather like this second example; they are neither explanatory nor corroborahle in the style of the physical sciences, yet they are supported sufficiently well to command widespread acceptance. Later I examine the part of this thesis which claims that evolutionary theorizing lacks the ability to predict, but here it is the different structure of explanation and mode of evidential undergirding which are purportedly characteristic of this theorizing which calls for comment.

(a) The Use of Narrative

Several decades ago Beckner¹ described a characteristic of evolutionary interpretations of the history of life which, in his opinion, inevitably marked much of the writing of paleontologists and historical geologists. It was a description which others have found to be fitting. For Beckner and his fellows the past is made intelligible largely through the use of narrative passages, together with loose argument, connecting occasional and brief attempts at deductive argument in the style of the physical scientist.² This emphasis upon narrative explanation is apparently made necessary by the uniqueness of the events which comprise the evolutionary history of living things; because events differ from one another in significant ways they cannot be instances of laws and most then be explained by pointing out and describing the sequence of circumstances which seem to have preceded or accompanied them.
It is worth noticing in passing, however, that narration might be widely employed in evolutionary interpretation for reasons other than the nature of the events being discussed. For one thing, the narrative may, on inspection, prove to he more a description of the scheme which unraveled a puzzle than an argument supporting the interpretation. The process of decipherment, unfolding "the context of discovery" as analysts of science would call it, may he mistaken for the "context of justification." This is particularly likely if one's writings are intended to instruct and to convince the reader by leading bins or her along the sort of path which the writer found useful in arriving at some particular insight. As another example, the complexity of the occasions being dealt with and the lack of so much desirable information in the fossil record might make the use of a highly-descriptive account convenient as an explanation sketch. It would appear then that the narrative form is sure to be a familiar one in the literature of evolution, as Beckner and those like him have claimed. The question remains whether the form is unavoidable whenever an understanding of evolution is attempted.

Let us first look briefly at the idea that evolutionary events are unique for this, we saw, was used as a constraint by some which they claimed prevented the use of explanatory schemes used in physical science. The difficulty which at once comes to mind is that "unique" must be defined by including the specifications under which the terns is to apply. Buddy Rich, for example, is unique in drumming skills but not in being American, male, or over 50 years of age. Likewise, the disappearance of the last saber-toothed tiger is unique in that it occurs only once but it is not unique if treated as an example of the disappearance of a life form by the processes of natural selection. An event's character then depends upon the scheme under which it is described.

If this is so, it is far from obvious that evolutionary explanations cannot be arrived at within which any historical event can be employed without the question of the event's uniqueness ever arising. In a similar way, whether an event is an instance of a law depends upon how specifically we describe it. Any event may he specified in such a way as to be non-recurring and thus an instance of none of the usual laws of science. Described, though, in suitable ways any event may become an example of one or more of these laws. It would seem, then, that description of evolutionary events might he developed which would enable its to see them as examples of evolutionary laws of some kind. If so, the thesis that evolutionary explanation does not employ laws is either true or false in fact but no principle seems to prevent the possibility.³

If there might he evolutionary laws the case for the necessity of narrative explanation, on the grounds that they can't exist, collapses. Those who defend this form of explanation most then argue that such laws are so rare that they can play little part in evolutionary understanding. We shall now see, however, that, if evolutionary laws are so difficult to come by, evolution would be devoid of explanation as much by narrative description as by covering laws! The reason is that narration seems to be impossible without at least a disguised utilization of law, a constraint which has been pointed out b various writers.⁴

Let us suppose that explanation in an historical area like paleontology means the presentation of a sufficient number of relevant circumstances preceding or accom panying an event, that is "E because C1, C2, Q3 . The
measure of sufficiency is that the event could reasonably have been predicted had we known C1, C2, C3 .... ; thus "If C1 , C2, C'. .. then E." The probability which we may claim for our prediction depends upon the number of relevant circumstances which our narrative provides. Dray, who argues for explanation in this style, calls this ground for F an "inference rule."⁵

Compare this with the covering law model employed in physical science: one or more laws L1 , L9, L3 ... together with a set of relevant circumstances C1, C2, C3... allows its to infer event E. (If the laws are statistical, we may conclude that there is a certain probability of F). Dray clearly wishes to remove laws from the explanatory schema and to replace them by a role for moving from the circumstances to the event directly, However, as Hemspel⁶ has noted, not only is the move often difficult or impossible, hot it seems apparent that we are merely moving from one form of empirical generalization to another. The inference role is less like a role in chess than a role such as meteorologists might use in discussing the weather; it is a sort of law experientially derived, subject to change when new insights in science alter our view as to which conditions are relevant to an event and modified each time the conditions which are described vary in number.

Looking at narrative accounts from a different perspective leads to similar conclusions. Let us suppose that we are offered an explanation of the origin of some property of a group of organisms such as Goudge's account of the origin among amphibians of limbs suited to locomotion on land. We are told a story of drought and of the necessity to find water which resulted in an advantage for these animals capable of moving from pool to pool, an advantage which by accident permitted them to remain on land. Unfortunately, as Ruse⁷ has noticed, the account provides no understanding of such things as how limbs might have developed, nor of why amphibians needed to remain in water initially yet could eventually remain on land. The probable explanation of these calls for the use of laws such as those of natural selection and genetics and of adaptive advantage. As these are all arrived at by modern studies and carried hack into the past they cannot be reduced to the language of historical narrative.
It appears that the case for narrative as the explanatory model for evolution is not easily made. Explanation by the use of scientific laws appears to be unavoidably present. Two further illustrations should re-enforce this observation.

(i) Inherent in narrative attempts at describing events there is a tendency toward classification in spite of frequent reference to the uniqueness of historical happenings. If this classification is to avoid arbitrariness and is to he explanatory it would seem that sonic general pattern of understanding must be employed; and this pattern can hardly he anything more than a covering law,

(ii) Narrative explanation also carries with it the isnplication that each step in an account can be shown to lead to the next, at least with reasonable likelihood. Surely this calls for the use of some covering law which makes the appearance of each stage predictable given what has preceded it.⁸

It is evident that whenever narration is employed in an explanatory role in evolution it reduces to either a simplified account, called for by the need for brevity or by a lack of information, or to a combined and informal presentation of the initial conditions arid lawful premises which appear to make some event which is of interest intelligible. All of these are necessary in telling the story of the history of life; hence the wide use of the style.

(b) Non-Scientific Explanation

We have been looking at the thesis that evolutionary explanation of the paleontologieal record is different from that found in the physical sciences but is nonetheless scientific Now we must explore briefly the quite different argument, offered by several writers, that evolutionary explanation of not only historical data but also of contemporary living things is not scientific at all.⁹ In essence this means that it is supposed that the theory contains no laws, that it lacks theoretical entities, and that the theory is not testable and consequently is not revisable in the light of experience. In examining this view, I comment only on Manser's version.

Manser begins by sharply distinguishing Darwin's concept of evolution from what we may call Mendelian genetics, later introduced into Darwinism as a specific assertion about the sneehanism of variation where the original concept had needed to say nothing. Evolution is explained in Darwinian terms, as Manser summarizes it, by structural variations which are inheritable appearing randomly with respect to any benefits they confer, by natural selection where the environment (internal or external) as related to some variation is more beneficial than to others, by selection conferring on those with more beneficial variation the capacity to survive and to reproduce themselves more successfully than others lacking these variations, by these benefits likely resulting in more numerous progeny, and by inheritance distributing the beneficial variation throughout the population.

As with any explanation of evolution, evolution is of course accepted as a fact by Darwinism; it states the way that environmental selection and variation are related and shows how it leads to the evolution of organisms. It is not, though, in Manser's opinion, a set of premises from which predictions may be made, with the result that it isn't testable. In form, it is a scheme of categories conceptually related to one another into which we place
examples derived from a study of living and fossil forms so that we explain them in evolutionary terms. It formulates no laws and its terms are defined circularly. For example, we cannot predict the fitness of an organism to survive, as the theory offers no criteria, but we can assert instead that an organism which has survived is fittest, and fittest because the organism had certain characteristics which were suited to the environment in a special way so that the organism gained an advantage over its competitors.

If Darwinian evolution is to show no more than how, after events have been discovered and described, they may be categorized so as to reveal their evolutionary relationship to one another, it is necessary that the scheme cannot be expressed in the theory form sketched in the first section of this paper. This is so because, should Darwinian be expressible by a set of axioms, the theorems deduced are predictions and thus are potentially testable. In fact, Darwinism can he expressed in just this fashion: in an important paper almost 30 years ago (and 16 years before Manser's papers), Mary Williams provided a short set of axioms which include, or from which can he deduced, all the statements of Darwinian evolution.¹⁰ The nonscientific appears to be scientific after all.

There is, though, a catch here because the theorems which Williams derived were so general as to he to all intents untestable. It would require a great deal of work to state an improved set of axioms necessary for deriving much more specific, and thus testable, consequences. The alternative is a less-rigorous, a rather intuitive, derivation of these predictions from the original set.¹¹ Surely that shouldn't bother us too greatly for much of even a "hard science" like physics is in the same position; for example, we explain empirical laws within Newtonian mechanics, just as Newton did in the Principia, in a quite intuitive and nonrigorous manner in our classes and textbooks.

Nonetheless it is a fact that many remain convinced, if I may judge from numerous letters and conversations, that evolution appears in too many ways to be untestable. Perhaps this is due to a lack of knowledge as to just what testability accrues to the intuitively-derived predictions of Darwinian theory, or of that theory cum genetic principles, as well as to the application of laws within evolution. We shall look at these accruals in due course, but, whatever the reason, a thesis such as Manser's meets with considerable sympathy. Others equally bothered have turned to Sir Karl Popper, the leading modern advocate of testability as the criterion demarcating scientific discourse, to determine whether evolutionary theory might be otherwise understood. With Popper they conclude that it is a metaphysical speculation.¹²

(e) Metaphysical Explanation

As is by now well-known, Popper opposes the view that science may properly ever claim to have grasped the essential character of nature's patterns and regularities. Likewise, he stands in opposition to the alternative instrumentalistic thesis that science shouldn't attempt to explain nature save in the sense of inventing whatever useful fictions result in correct prediction. His own view is that science properly makes tentative suggestions as to what is going on in the world, suggestions which may be true but at best can he shown to he corroborated by severe testing. At worst they are falsified by experience, with the advantage however of teaching us ways by which nature does not function. The Popperian view may then be called Jallibilism.¹³

The line between science and other claims to understand our world is now drawn in these terms. Science stands as the composite of actual and potential fallible explanations which are open to severe testing, that is testing which could well show them to be false. All else is unfalsifiableincluding essentialistic and instrumentalistic, as well as Popper's own, evaluations of how to do science. However, Popper is scarcely likely to treat Zen Buddhism and the hundreds of pages of defence of his fallibilistic model as on a par; we find that he does not, for he takes one to be far more open to critical application than the other. For example, his view of science may be compared with its competitors to determine which best fosters open-minded research and which hinders most the retention of error. Likewise, metaphysical speculations may he judged among other things, in terms of the degree to which they support science or suggest scientific theories and directions of scientific study.¹⁴

In this light we may understand Popper's comment that "Darwinism is not a testable scientific theory but a metaphysical research programme-a possible framework for testable scientific theories."¹⁵ We may also realize just why Popper has invested considerable effort into developing his own explanation of the trends found in the fossil record: a suggested improvement in presentday evolutionary theory which, in his opinion, cannot make sense of such directional sequences.

But why does Popper consider contemporary theory on evolution metaphysical rather than merely scientifically insufficient? Presumably because the theory is untestable in areas even where it seems to make sense. Popper provides several examples, each of which he feels exhibits a failure of the theory to predict and thus to explain (he believes that if we cannot say "If such and such had been the case then this would have been predicted," we cannot say "This occurred because such and such is the case").¹⁶

One example is the evolution of variety (speciation) where he thinks we can merely report that certain species were apparently adapted sufficiently to survive but we could not predict that these alone, or indeed that any, would have survived. Another is the idea which we mentioned earlier that fitness to survive (adaptability) is measured by actual survival but would not have been predicted. Lastly, he argues that we cannot predict any specific evolutionary change so that when we find sudden changes in fossil forms we can only claim that, in light of current doctrine, we should look for an explanation in terms of a missing record of small and accumulating mutational events.

Each of these is discussed at length in a recent paper by Ruse.¹⁷ As he properly points out, all that is necessary to refute Popper's thesis is to report actual predictions in each case which have been tested or which are open
to testing in some future research programs. This Rose does; consequently the illustrations point up issues which lie within science so that speciation, adaptability and rates of evolutionary change are not merely metaphysical concepts as Popper claims.¹⁸ I might add that this does not prevent the concepts being given additional metaphysical interpretations whose worth, or lack of it, must he assessed on appropriate grounds but that is quite another matter.¹⁹

In suns, then, Popper has failed to show that evolutionary explanation is either non-scientific or metaphysical on his own criteria. With Ruse I would put the failure down to Popper's being poorly informed about current work in evolution and not to his criteria. They remain invaluable tools for further work in demarcating science from other things.

(To be continued.)

REFERENCES

¹M. Beckner, The Biological Way of Thought, Columbia Univ. Press, New York, 1959.
²Compare TA. Coudge, The Ascent of Life, Univ. of Toronto Press, Toronto, 1961 and "Causal Explanations in Natural History," Brit. Jour. for the Phil. of Sci., Vol. 9, 1959-60, pp. 194-202: It. Burhenn, "Narrative Explanation and Redescription," Can. Jour, of Philosophy, Vol. 3, 12/73, pp. 419-425; DR. Kitts, The Structure of Geology, Southern Methodist Univ. Press, Dallas, 1977, pp. XV, 91-92; L. Goldstein, "A Note on Historical Explanation," Philosophy of Science, Vol.42,9/75, pp. 312-319; and SW. II. Dray, Laws and Explanations in History, Oxford Univ. Press, London, 1966. K. Popper, The Poverty of Historicism, Routledge & Kegan Paul, London, 1963, p. 108 refers to the uniqueness of evolutionary events but does not espouse narrative explanation. His position will he discussed later in this paper.
³D. Hall, Philosophy of Biological Science, Prentice-Hall Inc., Englewood Cliffs, NJ., 1974 suggests some of these points also.
4D. Hull, op. cit.; C. C. Hempel, Aspects of Scientific Explanation, Free Press, New York, 1965, pp. 44611 and his "Explanation and Prediction by Covering Laws" in B. Banmrin (ed., Philosophy of Science, Vol. 1, Inteescience Publishers, 1963, pp. 107-133; 11. Lehman, "On the Form of Explanation in Evolutionary Theory," Theon'a, Vol. 32, 1966, pp. 14-24; M.. Ruse, "Narrative Explanation Revisited," Can, Jour, of Philosophy, Vol. 4, 3/75, pp. 529-533 and his earlier "Narrative Explanation and the Theory of Evolution," Can. Jour, of Philosophy, Vol. 1, 9/71, pp. 59-74, "Is the Theory of Evolution Different?" Scientia, Vol. 106, 1971, pp. 765-783, 1069-1093, and The Philosophy of Biology, Hutchinson, London, 1973.
⁵Dray, Laws. Compare M. Scriven, "Explanation & Prediction in Evolutionary Theory," Science, Vol. 130, 28/8/59, pt, 477-482 and "Explanations, Predictions and Laws." In H. Feigl and C. Maxwell (eds.), Minnesota Studies in the Philosophy of Sciences, Vol.3, Univ. of Minn, Press, Minneapolis, 1962.
⁶Hempel, Aspects, p. 357.
⁷Ruse, "Narrative Explanation and the Theory of Evolution" and "Is the Theory of Evolution Different?.," pp. 1084-1090.
⁸See Hempel, Aspects, p.446.
⁹A. B. Manser, "The Concept of Evolution," Philosophy, Vol. 40, 1/65, pp. 18-34; AD. Barker, "An Approach to the theory of Natural Selection," Philosophy, Vol. 44, 10/69, pp. 271-290 (a sympathetic discourse (in Manser's paper); and J.J.C. Smart, Philosophy and Scientific Realism, Routledge & Kegan Paul, London, 1963. An attitude similar to Manser's is found in PA. Hayek, "Degrees of Explanation," Brit. Jour. for the Phil. of Sri., Vol. 6, 195,5-56, pp. 209227.
¹⁰M. Willianss, "Deducing the Consequences of Evolution: A Mathematical Model," Jouru. of Theor. Biol. , Vol. 29, 1949, pp. 343-385.
¹¹See M. Wilhams, "Palsifiahle Predictions of Evolutionary Theory," Philosophy of Science, Vol. 40, 1973, pp. 518-537.
¹²K. Popper, "Darwinism as a Metaphysical Research Programme" in PA. Schilpp (ed.) The Philosophy of Karl Popper, Vol. 1, Open Court Pub. Co., La Salle, Illinois, 1974, pp. 133-143 and his Objective Knowledge: An Evolutionary Approach, Oxford Univ. Press, London, 1975, pp. 242 ff.
¹³See my "Notes on the Predispositions of Scientific Thought and Practice," this journal, Vol. 24, 6/72, pp. 51-57 for an outline. Detail is provided in Popper's The Logic of Scientific Discovery, Hutchinson of London,
1959; in his Conjectures & Refutations, Routledge & Kegan Paul. London, 1963, pp. 66-96, 164-200, 253-292; in the Schilpp volumes (see note 12); in B. Magee, Popper, Fontana Books, Clasgow, 1975; and in B. Ackermaon, The Philosophy of Karl Popper, Univ. of Mass., Amherst, 1975.
¹⁴ Compare J . 0. Wisdom. ''Scientific theory: empirical Content, Embedded Ontology, and Weltsoischannrsg,'' Phil. Phenom. Research, Vol. 33, 1972, pp 62-77 and "Metaphysics & Verification- in John Wisdom, Philosophy & Psychoanalysis, Univ. of California, Berkeley 1969; P. Quay, "Progress as a Demarcation Criterion for the Sciences," Philosophy of Science, Vol. 41, 1974, pp. 154-170; "Popper's Account of Acceptability," Anal. Jour. Phil., 1971, pp. 167-176; C. Hartshorne "Present Prospects for Metaphysics," Monist, Vol. 47, 1963, pp 155210; K. Nielsen, "Metaphysics and Verification Revisited," Southwestern Jour. Phil., Vol. 6, 1975, pp. 75-94; II. Hochberg. "Metaphysical Explanation," Meta philosophy, Vol. 1, 1970, pp. 139-165. J. Walker "The Tolerability of Metaphysics," Internat. Phil. Quart., Vol. 13, 1973, pp. 5-2,3; and J.W.N. Watkins, "Confirmable and Influential Metaphysics," Mind, Vol. 67, 1958, pp. 344-365.
¹⁵Popper, "Darwinism," p. 134.
¹⁶Ibid., pp. 136-138.
¹⁷M. Ruse, "Karl Popper's Philosophy of Biology," Philosophy of Science, Vol. 44, 12/77, pp. 638-661.
¹⁸Compare M. Ruse, "Confirmation and Falsification of Theories of Evolution," Scientia, Vol. 104, 1969, pp. 329-357 and Z. Kochanski, "Con ditions and limitations of Prediction-Making in Biology,'' Philosophy of Science, Vol. 40, 1973, pp. 28-51.
¹⁹See M. Beckner, The Biological Way; Al. Crene & F. Mendelsohn (eds.), Topics in the Philosophy of Biology, Beidel, Dordrecht, 1976; 1). Hull, Philosophy; M. Ruse, Philosophy; J. Msusorl, Chance & Necessity, Collins, London, 1972; B. Bensch, Rio philosophy, Columbia Univ. Press, New York, 1971; W. Elsasser, Chief Abstractions of Biology, N. Holland Pub, Co., Amsterdam, 1975; F .Ayala and T. Dobzhansky, Studies in the Philosophy of Biology, Univ. of California Press, Berkeley, 1974; S.F. Smith, Philosophy of Biology, St. Johns Univ. Press, New York, 1967 and his Philosophical Problems in Biology, same publisher, 1966; 3,f. Crene, The Knower and the Known, Faber and Faber, London, 1976, her Understanding of Nature which is Vol. 23 of Boston Studies in the Phil. of Sci. and her Interpretations of Life and Mind, Routledge and Kegan Paul, London, 1971, which all contain discussions of metaphysical questions. From the large journal literature the following topics are illustrative: G. de Laguna, "The Role of Teleonomy in Evolution," Philosophy of Science, Vol. 29, 4/62, pp. 117-131; L. Wright, "Explanation & Teleology," Philosophy of Science, Vol. 39, 1972, pp. 2114-218 and Vol. 42, 1975, pp. 299-306; M Beckner, "Function and Teleology," Jour. Hst. Biol., Vol. 2, 1969, pp. 151-164; 1'. Scluevella, "Emergent Evolution & Reductionism," Scientia, Vol. 67, 1973, pp. 323-3,30; 54. Beckner "Metaphysical Presupposition ant] the Description of Biological Systems,'' Synthese, Vol. 15, 1963, pp. 260-274; A. Plamonstsin, "The Contemporary Reconciliation of Mechanism and Organicism," Dialectics, Vol. 29, 1975, pp. 213-221; H. Hein "The Endurance of the Mechanism-Vitalistic Controversy," Jour. Hist. Biol., Vol. 5, 1972, pp. 159-185; and F. Ayala, "Biology as an Autonomous Science," Amer. Scientist, Vol. 56, 1968, pp. 207-221.