Do mathematical objects exist after their definition?
106272
Do numbers exist independently from observers?
54262
When are infinities okay?
94433
Rigorous underpinnings of infinitesimals in physics
70332
Is there a third dimension of numbers?
144181
Given an arbitrary set $X$, can one always find an element outside $X$?
153969
The "elements" of a real number
94415
Existential import: in logic, do propositions default to true or false when objects in them do not exist?
119901
Why is variable called "variable" in mathematics if in fact it's immutable?
50602
Does uncountable summation, with a finite sum, ever occur in mathematics?
31212
The existence of the empty set is an axiom of ZFC or not?
111723
Can it be proven in $\sf ZF^{\neg\infty}$ that the sets $x_n=\{x_{n+1}\}$ do not exist?
90471
Can the limit of a product exist if neither of its factors exist?
38674
Do complex numbers really exist?
31392
Examples and Counterexamples of Relations which Satisfy Certain Properties
153976
Do complex quantities and irrational numbers exist in nature?
116355
Do singularities have a "real" as opposed to mathematical or idealized existence?
52682
Is the power set of the natural numbers countable?