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Philosophical aspects of logic and set theory; truth status of mathematical axioms; Philosophy of Mathematics; philosophical aspects of mathematics in general; relation of mathematics to philosophy; etc. Consider also posting at http://philosophy.stackexchange.com/, where philosophy-of-mathematics is one of the most popular tags.

241 votes
Accepted

Is the analysis as taught in universities in fact the analysis of definable numbers?

The concept of definable real number, although seemingly easy to reason with at first, is actually laden with subtle metamathematical dangers to which both your question and the Wikipedia article to w …
Joel David Hamkins's user avatar
148 votes
Accepted

Nontrivial theorems with trivial proofs

Bertrand Russell proved that the general set-formation principle known as the Comprehension Principle, which asserts that for any property $\varphi$ one may form the set $\lbrace\ x \mid \varphi(x)\ \ …
136 votes

Has philosophy ever clarified mathematics?

I find the case of Alan Turing's development of the concept of computatibility to be an example. Before Turing, the logicians had no clear concept of what it means to say that a function is computable …
72 votes

Nontrivial theorems with trivial proofs

Cantor proved that the set of real numbers is uncountable---it cannot be put in bijective correspondence with the natural numbers---but the proof is a simple diagonalization: if the real numbers could …
72 votes

Can a problem be simultaneously polynomial time and undecidable?

Consider the following simplified example of the same phenomenon, which many students find clarifying. Let $f(n)=1$, if there are $n$ consecutive $7$s in the decimal expansion of $\pi$, and otherwise …
Joel David Hamkins's user avatar
48 votes

Contemporary philosophy of mathematics

Let me mention a few current issues on which I have been involved in the philosophy of mathematics. Of course there are also many other issues on which people are working. Debate on pluralism. First, …
43 votes
Accepted

Why hasn't mereology succeeded as an alternative to set theory?

I have long found this question interesting, and in some recent joint work with Makoto Kikuchi, now available, we consider various aspects of the question of whether a set-theoretic version of mereolo …
Joel David Hamkins's user avatar
39 votes

Do set-theorists use informal set theory as their meta-theory when talking about models of ZFC?

The main fact is that a very weak meta-theory typically suffices, for theorems about models of set theory. Indeed, for almost all of the meta-mathematical results in set theory with which I am familia …
Joel David Hamkins's user avatar
36 votes
Accepted

Meta$^{n{-}th}$ mathematics

My opinion is that there is no crisp distinction between mathematics, metamathematics and meta-metamathematics, and the subjects thoroughly blend one into another in such a way that prevents any coher …
Joel David Hamkins's user avatar
30 votes

Should there be a true model of set theory?

Two weeks ago a conference was held on precisely the topic of your question, the Workshop on Set Theory and the Philosophy of Mathematics at the University of Pennsylvania in Philadelphia. The confere …
Joel David Hamkins's user avatar
28 votes

Ultrainfinitism, or a step beyond the transfinite

My view is that the large cardinal hierarchy already has all the principal features of the project you are proposing. Each of the large cardinal concepts can be regarded as corresponding to a certain …
Joel David Hamkins's user avatar
26 votes

Siegel zeros and other "illusory worlds": building theories around hypotheses believed to be...

I have heard that Jack Silver's discovery of zero sharp ($0^\#$) was part of his attempt to show measurable cardinals inconsistent. Instead of finding the long-sought-after contradiction, however, he …
25 votes

The Importance of ZF

There is a very active ongoing debate within set theory about whether mathematics needs new axioms, and philosophers of mathematics are weighing in on all sides. Relevant considerations include many v …
Joel David Hamkins's user avatar
24 votes

Logic in mathematics and philosophy

There is a general pattern of inquiry in mathematics and the sciences by which an investigation begins in philosophy, using philosophical ideas that may be initially quite vague, but which become incr …
Joel David Hamkins's user avatar
24 votes

Is platonism regarding arithmetic consistent with the multiverse view in set theory?

The view you are suggesting is something close to what is held by Solomon Feferman, who holds that the objects and truths of arithmetic have a definite nature that is not shared when one moves up to h …
Joel David Hamkins's user avatar

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