Hume's Principle requires the existence of the finite cardinals and their cardinal, but these are the only cardinals the Principle requires. Were the Principle an analysis of the concept of cardinal number, it would already be peculiar that it requires the existence of any cardinals; an analysis of bachelor is not expected to yield unmarried men. But that it requires the existence of some cardinals, the countable ones, but not others, the uncountable, makes it seem invidious; it is as if an analysis of people required that there be men but not women, or whites but not blacks. If we deprive the Principle of existential commitments, it will cease to yield Dedekind's axioms for the natural numbers and so fail a good test of material adequacy. But since there are cardinals no second-order theory guarantees, neither can the Principle be beefed up to require all cardinals.
References
[1]špace-9pt Barwise, J., Admissible Sets and Structures, Springer-Verlag, Berlin, 1975.
[2]špace-3pt Benacerraf, P., "What numbers could not be", Philosophical Review, vol. 74 (1965), pp. 47--73.
Mathematical Reviews (MathSciNet):
MR171702
[3]špace-3pt Boolos, G., "Saving Frege from contradiction", pp. 438--52 in Frege's Philosophy of Mathematics, Harvard University Press, Cambridge, 1995. Originally published in Proceedings of the Aristotelian Society, vol. 87 (1986/87), pp. 137--51.
[4] Boolos, G., "Nominalist Platonism", pp. 73--87 in Logic, Logic, and Logic, Harvard University Press, Cambridge, 1998. Originally published in Philosophical Review, vol. 94 (1985), pp. 327--44.
[5] Boolos, G., "On second-order logic", pp. 37--53 in Logic, Logic, and Logic, Harvard University Press, Cambridge, 1998. Originally published in Journal of Philosophy, vol. 72 (1975), pp. 509--27.
[6] Boolos, G., "To be is to be a value of a variable (or to be some values of some variables)", pp. 54--72 in Logic, Logic, and Logic, Harvard University Press, Cambridge, 1998. Originally published in Journal of Philosophy, vol. 81 (1984), pp. 430--49.
[7] Boolos, G., and R. Jeffrey, Computability and Logic, Cambridge University Press, Cambridge, 3d edition, 1989.
[8] Burali-Forti, C., "A question on transfinite numbers", pp. 104--11 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15
[9] Cantor, G., "Letter to Dedekind", pp. 113--17 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15
[10] Church, A., Introduction to Mathematical Logic. Vol. I, Princeton University Press, Princeton, 1956.
[11] Dreben, B., and J. van Heijenoort, "Introductory note to 1929, 1930, and 1930a", pp. 44--59 in Kurt Gödel, Collected Works, edited by S. Feferman et al., The Clarendon Press, New York, 1986. Publications 1929--1936.
[12] Hart, W. D., "Skolem's promises and paradoxes", Journal of Philosophy, vol. 67 (1970), pp. 98--109.
[13] Hart, W. D., "On an argument for formalism", Journal of Philosophy, vol. 71 (1974), pp. 29--46.
[14] Hart, W. D., "The potential infinite", Proceedings of the Aristotelian Society, vol. 76 (1975--1976), pp. 247--64.
[15] Hart, W. D., "Russell and Ramsey", Pacific Philosophical Quarterly, vol. 64 (1983), pp. 193--210.
[16] Hasenjaeger, G., "Sets, models and recursion theory", pp. 173--82 in On Löwenheim-Skolem-Type Insufficiencies of Second Order Logic, edited by J. N. Crossley, North-Holland, Amsterdam, 1967.
Mathematical Reviews (MathSciNet):
MR220583
[17] Henkin, L., "The completeness of the first-order functional calculus", The Journal of Symbolic Logic, vol. 14 (1949), pp. 159--66.
[18] Henkin, L., "Completeness in the theory of types", The Journal of Symbolic Logic, vol. 15 (1950), pp. 81--91.
Mathematical Reviews (MathSciNet):
MR12,70b
[19] Hilbert, D., "On the infinite", page 376 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15
[20] Hylton, P., Russell, Idealism, and the Emergence of Analyic Philosophy, Oxford University Press, Oxford, 1990.
[21] Löwenheim, L., "On possibilities in the calculus of relatives", pp. 228--51 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15
[22] Parsons, C., "Frege's theory of number", pp. 150--75 in Mathematics in Philosophy, Cornell University, Ithaca, 1983.
[23] Parsons, C., "Frege's theory of number", pp. 180--203 in Philosophy in America, edited by M. Black, Cornell University Press, Ithaca, 1965. Reprinted in Frege's Philosophy of Mathematics, Harvard University Press, Cambridge, 1995.
[24] Quine, W. V., "Ontological relativity and other essays", in Ontological Relativity, Columbia University Press, New York, 1969.
[25] Quine, W. V. O., Methods of Logic, Henry Holt & Company, New York, 1950.
[26] Quine, W. V. O., Set Theory and Its Logic, Harvard University Press, Cambridge, 1969.
Mathematical Reviews (MathSciNet):
MR43:37
[27] Resnik, M. D., "Second-order logic still wild", The Journal of Philosophy, vol. 85 (1988), pp. 75--87.
[28] Skolem, T., "Logico-combinatorial investigations in the satisfiability or provability of mathematical propositions: A simplified proof of a theorem by L." Löwenheim and generalizations of the theorem, pp. 252--63 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15
[29] Skolem, T., "Some remarks on axiomatized set theory", pp. 290--301 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15
[30] Weyl, H., Philosophy of Mathematics and Natural Science, Princeton University Press, Princeton, 1949. Revised and augmented English edition based on a translation by Olaf Helmer.
[31] Zermelo, E., "Investigations in the foundations of set theory I", pp. 199--215 in From Frege to Gödel. A Source Book in Mathematical Logic, 1879--1931, edited by J. van Heijenoort, Harvard University Press, Cambridge, 1967.
Mathematical Reviews (MathSciNet):
MR35:15