In philosophy of mathematics he advocated the view of formalism rather than platonism or intuitionism. Sidgwick considers three such procedures, namely, rational egoism, dogmatic intuitionism, and utilitarianism. He has defended ethical intuitionism, direct realism, libertarianism, veganism, and philosophical anarchism. He was also critical of irrationalism and intuitionism. These included intuitionism, formalism, and predicativism. On this definition, moral sense theory is a form of ethical intuitionism. He was the founder of the mathematical philosophy of intuitionism. Ethical intuitionism was first clearly shown in use by the philosopher Francis Hutcheson. Kronecker's finitism made him a forerunner of intuitionism in foundations of mathematics. For more see constructive mathematics and Intuitionism. There may be issues of arbitrariness or "sloppy intuitionism" lurking there. Soon he became a known mathematician specializing in the fields of ultrafinitism and intuitionism. Brouwer's philosophy, called intuitionism, started in earnest with Leopold Kronecker in the late 1800s. Robert Audi is one of the main supporters of ethical intuitionism in our days. Michael Huemer's book "Ethical Intuitionism" (2005) also provides a recent defense of the view.