Re: Hierarchy/Hierarchies of Scientific Knowledge

Greg,
    I don't know what philosophers of science say about it but I can comment on how we as practitioners of science think about it, though we don't write about it. It's rather informal and not formally identified, for the most part.
    I would say there are various criteria for setting hierarchies in science. One is the degree of abstraction. A foundational level would be a physical description of the system whereas more abstract levels deal with the implications. In my own field of semiconductors, this would for example, mean that a detailed derivation of the density of states of electrons is a foundational level but a more abstract level would deal with the application to conductivity in a transistor. In biology, the foundational level might be the structure of DNA whereas its functionality is a higher level.
    A second partitioning is breadth of application. Again from semiconductor science, a specific study of arsenic impurities in silicon is a narrow, but important application, whereas a study that applies to any impurity in any semiconductor is more broadly applicable and at a different functional level.
    To use Donald Mackay's example of a sentence written in chalk on a blackboard, the physical description is pretty basic. In principle, you could cite the physical location and type of each atom, though it would be rather tedious to use a fine grid and cite each of the 10^24 atoms. That's a complete description at that level. Another level would be a description of the forces, such as the bonding structure, connecting the atoms. A more abstract level is the form and shape delineated by the chalk atoms. A whole new class of meaning deals with the interpretation of those shapes as a linguistic alphabet, a vocabulary of words, and finally a meaning(s) of the sentence. These levels of meaning depend on the conventions established by a group of people that assign a pre-determined meaning to letters, words, and grammar. Of course, the physical descriptions depended on the conventions and interpretations of physicists and chemists. Any level of meaning depends on an external body of information brought to bear on that system. And a description of one level helps to understand that of another level. In this case, the meaning of the sentence helps to understand the reason for the specific physical location of the atoms.
    The core premise of ID is often explained in these terms. The pattern of the information content in terms of the physical sequence and state of biomolecules in a living cell can be understood by the meaning and function of the system as a whole. The difference of course is in the feedback loop. For the atoms of chalk on the blackboard, there is no feedback mechanism whereby the meaning of the sentence can influence the positions of the atoms. For genetic material, there is a feedback loop whereby the probability of propagation through reproduction is influenced by the precise state of the biomolecular system. The argument is all about whether that feedback system is sufficient to explain the resulting pattern.
    And that leads me to the insufficiency of Mackay's hierarchical levels of meaning. As Keith pointed out, his approach is very helpful to show how a 'complete' explanation at one level does not precule or invalidate an explanation at another level. On the other hand, he offers no way of knowing whether additional levels exist or when a set of levels is complete. Neither is there a general way of validating a level of meaning. Each level of explanation must be validated by means of methodologies appropriate to that genre.

    Randy
  ----- Original Message -----
  From: Gregory Arago
  To: asa@calvin.edu
  Sent: Saturday, May 06, 2006 9:10 PM
  Subject: Hierarchy/Hierarchies of Scientific Knowledge

  In the thread on emergent properties, the words 'hierarchy' and 'hierarchical' have come up. This seems to suggest something that comes before or after, below, higher or above, primary, secondary, etc. Could folks at ASA help by describing/explaining what kind of hierarchy or hierarchies are said to exist in scientific knowledge?

  I found the paragraph by Keith Miller below and also Randy's opening post quite fascinating.

  Kind Regards,

  Greg

  "For me one of the fundamental perspectives is that an internally
  complete description of a system at one level does not in any way
  deny the validity of another different and non-contradictory
  description at another level. There can be several internally
  complete levels of description within the broad umbrella of science.
  At a yet higher level, the whole hierarchy of scientific descriptions
  become one type of understanding of reality that can be (at least
  theoretically) complete, but yet cannot exclude the existence of
  another equally valid, equally true, and non-conflicting understanding." - Keith Miller

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Received on Mon May 8 21:24:16 2006