Kronecker was primarily an arithmetician and. algebraist. Heis biggest contribution to mathematics was in the field of elliptical functions, the theory of algebraic equations, and the theory of algebraic numbers. For example, Kronecker's theory of algebraic magnitudes (1882). Thi theory revolves around algebraic numbers, "which are real numbers for which there exists a polynomial equation with integer coefficients such that the given real number is a solution. Algebraic numbers include all of the natural numbers, all rational numbers, some irrational numbers, and complex numbers of the form pi + q, where p and q are rational, and i is the square root of −1." (https://www.britannica.com/science/algebraic-number). Furthermore, "he was the first to doubt the significance of nonconstructive existence proofs (proofs that show something must exist, often by using a proof through contradiction, but that give no method of producing them)." (https://www.britannica.com/biography/Leopold-Kronecker). v(https://www.google.com/url?sa=i&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FLeopold_Kronecker&psig=AOvVaw3rIwdpu8LAeqKR4vvg1tbU&ust=1586205300510000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCPCYhq-R0ugCFQAAAAAdAAAAABAD).