The “required reading list” for philosophy tends to start with the ancient Greeks, and then it skips to the modern period. Much of the best modern metaethical philosophy (between the 17th and early 20th centuries) involved moral skepticism. In particular, Thomas Hobbes, David Hume, and Frederich Nietzsche.
Thomas Hobbes has been described as a “conventionalist.” We will say that something is “right” if it is agreed upon. In particular, he suggests that we should agree to laws that are enforced by the sovereign because without laws life will be “poor, nasty, brutish, and short” (Leviathan, VIII). Rather than provide proof that a life that is “poor, nasty, brutish, and short” lacks intrinsic value or promotes something of intrinsic disvalue, Hobbes assumes that we tend to have a personal interest in avoiding such a situation, so we can all agree to have laws without relying on metaethics. Hobbes metaethical position is precisely that we need not discuss whether or not anything of intrinsic importance really exists.
Many philosophers assume that Hobbes was a nihilist, and his philosophy is certainly consistent with nihilism (the idea that nothing has intrinsic importance). However, it is also consistent with agnosticism concerning moral reality.
David Hume took metaethical skepticism a step further than Hobbes by questioning moral reality entirely. Hume was an empricist, so the only evidence that he would consider relevant is empirical evidence (observation). He questions how it is possible that we can observe a fact and somehow infer from that observation what ought to be. (How do we derive an “ought” from an “is?”)
In Hume’s On a Treatise of Human Nature, he argues that our moral beliefs are derived from our sentiments, and then he argues that our sentiments are irrelevant to truth and falsity. In other words Hume agrees that we must psychologically agree to moral truths despite the fact that we actually have no evidence of any moral truths:
Now ‘tis evident our passions, volitions, and actions, are not susceptible of any such agreement or disagreement; being original facts and realities, compleat in themselves, and implying no reference to other passions, volitions, and actions. ‘Tis impossible, therefore, they can be pronounc’d either true or false, and be either contrary or conformable to reason. (Book III, Part I, Section 1)
He says that we can have no moral truths even though our passions seem to relate to morality somehow because passions cannot be said to be true or false and passions do not refer to anything else. It should be noted that the Stoics would disagree with this statement because when we are angry, for example, we require a belief. “You unjustly killed a human being” is the kind of belief that would incite anger. Anger cannot be understood as a thoughtless feeling because that would just be a general state of anxiety. Our suffering also appears to require some thoughts. Bodily pain in and of itself can be ignored when we are appropriately hypnotized, and the most painful forms of suffering involve the belief that something terrible has happened. Finding out that a loved one has died, for example, can cause pain with no physical basis. The belief is certainly tied to the pain.
Hume admitted that as human beings who have experienced pleasure and pain, we have no choice but to agree to pleasure and pain as our “ultimate ends.” Hume argues that we psychologically take pleasure and pain to be our ultimate ends in a similar way that Aristotle argues that happiness is our “final end,” and it amounts to just about the same thing:
It appears evident that—the ultimate ends of human actions can never, in any case, be accounted for by reason, but recommend themselves entirely to the sentiments and affections of mankind, without any dependance on the intellectual faculties. Ask a man why he uses exercise; he will answer, because he desires to keep his health. If you then enquire, why he desires health, he will readily reply, because sickness is painful. If you push your enquiries farther, and desire a reason why he hates pain, it is impossible he can ever give any. This is an ultimate end, and is never referred to any other object. (An Enquiry into the Principles of Morals, appendix 1, V.)
It is important to note that Hume still won’t think it is literally true that “pleasure is good” or “pain is bad.” Why he can’t make this leap is due to his empiricist convictions that introspection can’t give us evidence for the truth and that objects of introspection are irrelevant to the truth. Although we might want to say, “The experience of pleasure is experienced as being intrinsically good,” Hume will insist that there is nothing true or false about pleasure, and pleasure cannot refer to anything true.
Frederich Nietzsche presented various arguments involving metaethical skepticism. He argued (1) that our ideas of actions fail to account for the indefinite complexity of the situation, (2) that language fails to account for the indefinite complexity of moral reality, (3) that language used to describe our psychological states is inadequate, (4) morality isn’t universal.
Our ideas of actions can fail to account for the indefinite complexity of the situation because of the inadequacy of language. We think in simple terms, such as “killing, self-defense, and stealing” for actions involving indefinitely complected situations. To consider the importance of the situation to action, consider that the action “cut a man open” might sound wrong, but given the situation of being a surgeon trying to help a patient, it is considered perfectly moral. Nietzsche believes that every object and situation is unique, so words are hopelessly inadequate. We could use this line of thinking to agree that a virtuous person will know “the best course of action” based on the exact situation at hand, and we have no right to judge people unless we also understand the exact situation at hand.
The fact that language fails to account for the complexity of our mental states for the same reason that it fails to account for the situation—our mental states are just as complected as physical states. We use terms like, “belief” and “desire” to understand motivation, but these terms are oversimplifications. We cannot judge proper mental actions (proper beliefs, desires, and emotions) just like we cannot judge the proper physical actions. We also tend to be very interested in knowing the person’s intentions when we judge him or her morally. (Is the surgeon trying to help a patient, or is he trying to hurt someone?)
Nietzsche’s skepticism does raise some good questions, and it raises serious worry that we can ever achieve a perfect understanding of moral truth. However, he does not argue that there are no moral facts independent of our beliefs. We might have no choice but to endlessly try to improve our understanding of moral facts. We might still be justified to have moral beliefs despite the fact that it will be inadequate to some extent.