John Stuart Mill, a 19th-century philosopher, is known for his utilitarian ethical theory, which centers on the principle of maximizing happiness or pleasure and minimizing pain or suffering. In the quote you mentioned, Mill is expressing the idea that the quality of one's experiences and intellectual capacity is more important than the quantity of pleasure one experiences.
When Mill refers to a "fool satisfied" and a "pig satisfied," he is using these terms metaphorically to make a point about different levels of happiness and contentment.
A fool satisfied: Mill is referring to a person who may be ignorant, uneducated, or lacking in critical thinking skills. This person might find contentment and pleasure in simple, base, or shallow pursuits, but their satisfaction is not rooted in a deeper understanding or appreciation of life. Their happiness might be fleeting, and they might not be aware of more profound aspects of existence.
A pig satisfied: Mill uses the pig as a symbol of an animal driven solely by its instinctual desires. Pigs are often associated with indulgence and hedonism. So, when Mill talks about a pig being satisfied, he means a creature that seeks only immediate and sensual pleasures, without any higher intellectual or moral considerations.
In contrast to these examples, Mill argues that it's better to be "Socrates dissatisfied" or a "human being dissatisfied" because they possess higher intellectual and moral faculties. Socrates, a renowned philosopher, valued wisdom and the pursuit of knowledge above mere pleasure. A human being, endowed with rationality and moral consciousness, has the capacity to reflect on life's complexities and seek more profound forms of satisfaction and fulfillment.
Mill's point is that intellectual and moral pursuits, even if they may lead to some dissatisfaction or discomfort, are superior to shallow pleasures. The quest for knowledge, personal growth, and the pursuit of higher values can lead to a more meaningful and fulfilled life, even if it involves moments of dissatisfaction or challenges along the way.