Letter to the Editor
MORE ON APPARENT-AGE THESIS
I have recently re-read Thomas Leith's paper on the apparent-age thesis (JASA, December 1965), along with the critical letters and his reply (JASA, June 1966). 1 still find the course of the argument puzzling in several ways. I will deal here with only one of them.
Professor Leith apparently believes that there are certain propositions such that "any evidence appropriate to [them] is at the same time both evidence corrobrating and evidence falsifying [them]" (June, p. 63). It is not clear, however, just what be takes to be the significance of this alleged fact. In some places he says that such propositions are "logically impossible," "absurb," and "irrational" (e.g., December, pp. 118-120, June, p. 63). Later in his paper, however, he says that some such propositions (e.g., the apparent-age thesis) "might well be meaningful," and he apparently also believes it to be logically possible that we should know the apparentage thesis to be true, perhaps by revelation. "But," he continues, "if we claim to have this knowledge we must recognize that it is not meaningful within any present or future science (it is there logicaHy impossible) . . . (December, p. 121).
Now, on their face these two sorts of claims appear to be just contradictory. In the usual sense of "logically impossible" it is not possible that we should know a logically impossible proposition to be true, but revelation or otherwise, for none of them are true. Presumably, however, we are to interpret Professor Leith as attempting to formulate some specially restricted "scientific" sense of terms such as "logically impossible," etc. It is just here, however, that I am puzzled, for I find it difficult to imagine just what this new sense might be. In particular, I do not understand how a proposition can be meaningful and perhaps true while it remains logically impossible and meaningless "within" any present or future science. And this is because I do not know how to discover (or how Professor Leith discovers) when a given proposition is "within" science and when that same proposition is outside. I do not know what he means by a proposition's being "within" a science.
Only one conjecture suggests itself to me at this point. Perhaps a proposition is "within science" if and when scientists use it or take account of it in their scientific work. And perhaps Professor Leith means to say that certain propositions which we can understand and perhaps even know to be true are such that scientists either do not or should not take account of them in their scientific work. (Such a proposition will then be said to be "meaningless" within science, and "logically absurd" in the special scientific sense of that term.) If this is Professor Leith's claim I think I understand it, but I find it rather uncomplimentary to the scientific enterprise. Perhaps I can explain why.
I do not claim to be a scientist (my salary is not budgeted to a science department), but, so far as I know, this fact does not prevent my use of any scientific procedure, proposition, or hypothesis in my own cognitive endeavors. I feel free to use any of these so far as my own technical and intellectual abilities allow. And I also feel free to use anything else which I happen to know. If "Leith's Law" is correct, however, then scientists are prohibited from using some of the things which they may know, although they are not, of course, authorized to use anything forbidden to the rest of us. Clearly, then, scientists are in a disadvantaged position. But if they abandon the claim to be scientists, then they could escape from Leith's Law. They would still be able to do all the things they did before (their technical and intellectual capacities would be unchanged), and, in addition they would be free to use whatever other cognitive resources they might possess, resources whose possibility Professor Leith himself acknowledges. This certainly appears to me to be a choice in which all the intellectual advantages lie on one side, and therefore to be a choice over which a rational man need not hesitate unduly.
Either, then, I do not understand what sense Professor Leith is trying to give to expressions such as "logically absurd," "meaningless within science," etc., or else he gives us a clear reason for ceasing to be scientists (of course, in his sense of "science").
George I. Mavrodes
Depart. of Philosophy
The University of Michigan, Ann Arbor, Mich.