The purpose of the succeeding sections is to find a definition that is equivalent to this where it is applicable but that does not require a specific choice of basis and that can also more easily be applied to infinite-dimensional settings where the usual basis concepts (Hamel basis) may be ill-behaved. Not requiring a specific basis is useful from a theoretical point of view since while every vector space has a basis, not all bases are necessarily constructible, and moreover that result itself depends on the acceptance of the axiom of choice, which may be rejected in some systems of mathematics. Also, it is useful to find an abstract construction for analysis from the point of view of category theory—the theory of the very zoomed-out "big picture of maths" and how all mathematical objects relate to each other in a very general sense. A very important real-life use for having such a definition can be found in quantum mechanics: the tensor product in this form allows us to talk of the wave function of a system of two particles as an abstract Hilbert space vector without having to specify a particular basis of observables.