mps@duke.cs.duke.edu (Michael P. Smith) (08/08/87)
In article <3728@watdcsu.waterloo.edu> dmcanzi@watdcsu.UUCP (David Canzi) writes: >Let's say that you define truth something like this: Statement X is >true iff statement X satisfies condition Y. In order to apply this >definition to determine whether X is true, one must determine whether >the statement "Statement X satisfies condition Y" is true. > >How do you do that? > You start by distinguishing between a *definition* and a *criterion*. A definition tells you what something is, not necessarily how to recognize it. It is clear that you want a criterion for determining whether a statement is true or false. First, I doubt that there is a general criterion for truth, any more than there is a general criterion for health. Doubtless you could think of a general definition of health, but when it comes to recognizing healthy trees, spiders, gerbils and people it's time to call in the specialist. Similarly, it is the business of the various specialized sciences to tell us how to evaluate such claims as This solution is acidic. The Crab Nebula is the ghost of a super-nova. The halting problem is undecidable. Alzheimer's disease is caused by a virus. and so on. Next, in order to apply the criterion "X is true iff Y" you must be able to recognize when Y is true. This is not circularity, but recursion. Scientific training consists in large part of increasing the range of evaluatable statements by extending these criterial chains. An interesting problem which has fascinated philosophers for centuries is the identification of the base of the recursion. It seems that there must be statements whose truth is recognizable without further ado, the primitives upon which our more sophisticated recognitional capacites are based. This is one meaning of the phrase 'self- evident'. In the past, many have thought that such primitives should be fixed and common to all, and that their status as self-evident should be self-evident as well. This complex of views is known is known in epistemology as 'foundationalism'. Lately some philosophers have called themselves 'weak foundationalists'. They accept some recursive structure for knowledge, but reject some of the traditional assumptions about self-evidence. ---------------------------------------------------------------------------- "Science is differentiated from the older myths not by being something distinct from a myth, but by being accompanied by a second-order tradition -- that of critically discussing the myth." K. Popper Michael P. Smith ARPA: mps@duke.cs.duke.edu ----------------------------------------------------------------------------
franka@mmintl.UUCP (Frank Adams) (08/11/87)
In article <3728@watdcsu.waterloo.edu> dmcanzi@watdcsu.UUCP (David Canzi) writes: >Let's say that you define truth something like this: Statement X is >true iff statement X satisfies condition Y. In order to apply this >definition to determine whether X is true, one must determine whether >the statement "Statement X satisfies condition Y" is true. > >How do you do that? Strictly speaking, it would seem that one must instead define: Statement X is true iff statement X passes test Y. Then to see if X is true, one must perform Y; this no longer involves evaluating the truth of any sentence. Note that to test the truth of statement X, we *apply* the definition. This is not the same as plugging statement X into the definition and seeing if a true statement results; it is instead applying test Y. (None of which should be taken as implying that any such test Y exists.) -- Frank Adams ihnp4!philabs!pwa-b!mmintl!franka Ashton-Tate 52 Oakland Ave North E. Hartford, CT 06108