Epistemology is the branch of philosophy that studies the nature of knowledge, including its sources, limits, and validity.

Socrates was known for his skeptical approach to knowledge, famously stating, "I know that I know nothing".

Skepticism is the philosophical position that knowledge is impossible or unreliable.

John Locke argued that all knowledge is derived from sense experience, which he called "impressions".

Rationalism is the philosophical position that knowledge is innate, rather than derived from sense experience.

Descartes famously said, "Cogito, ergo sum" (I think, therefore I am), expressing the idea that the existence of one's own consciousness is the only indubitable truth.

Dualism is the philosophical position that the mind and the body are distinct substances.

Baruch Spinoza argued that the mind and the body are one and the same substance, which he called "God or Nature".

Materialism is the philosophical position that the world is fundamentally made up of matter.

George Berkeley argued that the world is fundamentally made up of ideas, rather than matter.

Agnosticism is the philosophical position that the existence or non-existence of God or ultimate reality is unknowable.

Friedrich Nietzsche argued that the world is ultimately meaningless, and that we should embrace this meaninglessness and create our own values.

Intellectualism is the philosophical position that the good life is achieved through the pursuit of knowledge.

Epicurus argued that the good life is achieved through the pursuit of pleasure, but he also emphasized the importance of moderation and avoiding pain.

Eudaimonia is the Greek term for the good life, and it is often translated as "happiness" or "flourishing". Eudaimonia is typically understood as a state of well-being that is achieved through the pursuit of virtue.