John Stuart Mill: The Dangers Of Intuitionism

knowledge,” (CW, I.233) or, as he also calls it, “intuitionism,” which was espoused in different ways by Kant, Reid, and their followers in Britain (e.g. Whewell and Hamilton). Though there are many differences among intuitionist thinkers, one “grand doctrine” that Mill suggests they all affirm is the view that “the constitution of the mind is the key to the constitution of external nature—that the laws of the human intellect have a necessary correspondence with the objective laws of the universe, such that these may be inferred from those.” (CW, XI.343). The intuitionist doctrine conceives of nature as being largely or wholly constituted by the mind rather than more or less imperfectly observed by it. One of the great dangers presented by
this doctrine, from the perspective of Mill’s a posteriori school, is that it supports the belief that one can know universal truths about the world through evidence (including intuitions or Kantian categories of the understanding) provided by the mind alone rather than by nature. If the mind constitutes the world that we experience, then we can understand the world by understanding the mind. It was this freedom from appeal to nature and the lack of independent (i.e. empirical) checks to the knowledge claims associated with it that Mill found so disturbing.
Questions of ultimate ends don’t admit of ‘proof’ in the ordinary meaning of that term. It’s true of all first principles—the first premises of our knowledge, as well as those of our conduct—that they can’t be proved by reasoning. But the first principles of our knowledge, being matters of fact, can be the subject of a direct appeal to the faculties that make judgments of fact— namely our ·outer· senses and our internal consciousness.
For Mill, human knowledge is always fallible and always incomplete. Mill maintained that inductive logic is the true basis of knowledge. Mill sees experience