Intuitionism says that "good" is an indefinable notion. The basic moral truths are objective; they hold independently of what anyone may think or feel. We should pick our moral principles by following our basic moral intuitions."Good" is indefinable and objective
These questions are about Chapter 4 of Harry Gensler's Ethics: A Contemporary Introduction (Routledge: 1998 and 2011).
Intuitionism makes three claims: (1) "Good" is indefinable, (2) there are objective moral truths, and (3) the basic moral truths are self-evident to a mature mind. Let me explain these claims.There are self-evident moral truths
1. "Good" is a simple, indefinable notion. Suppose that someone defines "good" as "socially approved." We should ask, "Are socially approved things necessarily good?" The answer clearly is "no," which refutes the definition. We can refute other definitions of "good" in a similar way. Since "good" is indefinable, we can't prove moral conclusions from non-moral premises alone.
2. There are objective moral truths -- moral truths that don't depend on human thinking or feeling. "Hatred is wrong" is an example. Hatred is wrong in itself. It would still be wrong even if everyone approved of it. It's an objective truth that hatred is wrong.
Objections to intuitionism
3. The basic moral principles are self-evident truths -- known truths that require no further proof or justification. To apply these to concrete actions requires further information; it's never self-evident what we ought to do in a concrete situation.To arrive at the self-evident principles of morality requires reflection and intellectual maturity. The test of such principles isn't their initial plausibility, but whether a careful examination uncovers implications that clash with our intuitions.
Intuitionism, despite its initial plausibility, has some problems. In math, principles claimed to be self-evident are precise and largely agreed on by the experts. In ethics, principles claimed to be self-evident are vague and widely disputed. Intuitionists themselves disagree widely about what is self-evident.
Moral intuitions come largely from social conditioning, and vary greatly between cultures. So it's hard to believe that such intuitions are a reliable guide to objective moral truths. And appealing to intuitions can lead to an early stalemate on moral issues -- as when we argue with someone who has racist intuitions.