In 1739 Hume discusses the problem in book III, part I, section I of his work, A Treatise of Human Nature:
In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary ways of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when all of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, ’tis necessary that it should be observed and explained; and at the same time that a reason should be given; for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it.
For thousands of years philosophers and thinkers have asked the questions such as “What should I do?”, “What should be my purpose?”, “What is the meaning of life?”. Even after all this time, people still ask these questions, and do not come up with self satisfying answers. David Hume recognized that one cannot deduce what one ought to do from what is.
For example, you cannot deduce that your hair should look neat and clean from the observation “I have thick dark brown hair.”. So how can one ever make a statement proclaiming what one should do?
Indeed, it is true that it cannot be deduced what one ought to do from merely what is. “Should” is a declaration that it is best for a thing to act or be some way in order to achieve a particular goal. There is always a goal, frequently implied. Your mother may have told you “You should brush your teeth after breakfast and before bed time.”. You asker her “Why?”, and she replied “So that your teeth don’t rot away.”. You asked “Why?” again, and she said “So you look healthy and can digest food properly.”. You asked “Why?” again, and she replied “So people will enjoy looking at you and making friends with you, and so that you don’t die early from malnutrition.”. You asked “Why?” again, and she was stumped, and replied “Because mother says so, now brush your teeth or I’m going to have daddy make you.”. Weren’t you smart, if there is no basis reason to brush your teeth, then how can she be correct in making you brush your teeth before going to bed? Before being able to decide what one should do, one first needs a goal.
There is no universal goal. It is not satisfactory to include what one ought to do in your definition of what one is. Rand tried to do this with her concept of a “proper man”. There is no goal prescribed by properties of the universe. No scientist will ever deduce what one should do from discovering the properties of elemental components of the universe. Nor will a religious person ever satisfactorily discover a worthwhile goal from some proposed God. Lacking evidence, a religious person accepts a proposed God’s moral commands. They then frequently claim that a non-believer lacks morality. But their reason for acceptance of the moral commands are baseless: still the same problem.
How do we come about acquiring a goal, one’s first goal, one’s primary goal, and have a satisfactory logically valid reason for having it? It is impossible, unless you finally accept that your first goal is baseless. The meaning of life only exists as chosen by the individual. “The meaning of life”, your goals, are chosen by you. One’s only defence to someone’s criticism is “These are the goals chosen and that is how it is.”.
So in this way, one can have goals. Once can then build a collection of behaviours and actions to perform and avoid in various contexts in order to accomplish one’s goals. This collection is one’s morals.
Many individuals have morals that guide each of them to perform actions that are mutually beneficial. Rand’s morals to act in one’s own rational self interest is an excellent example. Given that one’s goal is to live a healthy happy life long term:
Through specialization comes increased productivity. Alone, an individual must do everything required to survive, gathering food, water, and maintaining one’s shelter, leaving little room for specialization. In a free market economic system the products of one’s labour can be exchanged for what one desires. One can specialize in growing corn, and produce incredible saleable value in the free market, then purchase more items and services than one could create and perform by oneself. Hence producers and traders have generally mutually beneficial relationships.