Are mathematical objects invented or are they discovered?

Since we’ve had quite an influx of fresh jellies lately, I thought I might be forgiven if I trotted out something of a rehash of an older question of mine.

Is math “all in the mind” (in which case one may perhaps wonder why bits of it often turn out to be useful for physics many years after their invention, or whether basic arithmetic is not in some sense inevitable) or can we posit a sort of timeless “being-ness” for sets, numbers, geometric figures, etc..?