A Review of Kit Fine's The Limits of Abstraction, 2002, Oxford, Oxford University Press.
Summary of ContentsKit Fine's recent The Limits of Abstraction, an extended version of his [1998] paper, contains four chapters. The first two deal with philosophical aspects of abstraction, while the latter two provide the formal framework for a general theory of abstraction. Here we focus on the philosophical material, and, given the depth and complexity of the material, cannot attempt even a superficial summary of the entirety of the philosophical material. Thus, we content ourselves with sketching the contents. Two particular issues will then be examined in greater detail.A theory of abstraction is, broadly construed, any account that reconstructs mathematical theories using second-order abstraction principles of the form: §xFx = §xGx ↔ E(F, G) (We ignore first-order abstraction principles such as Frege's direction abstraction.) The function ( §) occurring on the left-hand side of the biconditional provides objects corresponding to the concepts serving as the arguments of the function, and the identity conditions for the objects so introduced (the abstracts) are given by the equivalence relation E. The most notorious instance of a second-order abstraction principle is Frege's Basic Law V:which, infamously, is inconsistent.There has been a resurgence of interest in abstractionism. Neo-Fregeans have abandoned BLV in favour of (presumably consistent) abstraction principles, each delivering a particular mathematical theory. For example, Hume's Principle:[F ≈ G abbreviates the second-order formula asserting the equinumerousity of F and G] allows one to reconstruct second-order Peano arithmetic. Examining how far such a piecemeal approach to foundations can take us is currently an active and fruitful research project. Fine's approach is different. Instead of worrying over the acceptability of particular abstraction principles, or formulating principles that allow for the reconstruction of his favourite mathematical theories, Fine provides a general account of abstraction.