Epistemology is the branch of philosophy that studies the nature of knowledge, justification, and rational belief.

According to the traditional definition, knowledge is justified true belief. This means that in order to know something, you must believe it, it must be true, and you must have a justification for believing it.

The Gettier problem is a problem in epistemology that challenges the traditional definition of knowledge as justified true belief. The problem arises from cases where someone has a justified true belief, but they do not know that it is true.

One solution to the Gettier problem is to add a new condition to the definition of knowledge, such as the condition that the belief must be undefeated by any possible evidence.

A priori knowledge is knowledge that is known to be true without the need for experience. A posteriori knowledge is knowledge that is acquired through experience.

A priori knowledge is knowledge that is known to be true without the need for experience. Examples of a priori knowledge include the laws of logic and the fact that 2 + 2 = 4.

A posteriori knowledge is knowledge that is acquired through experience. Examples of a posteriori knowledge include the fact that the Earth is round, the fact that the sun is a star, and the fact that humans are mortal.

Analytic statements are statements that are true by definition. Synthetic statements are statements that are true in all possible worlds.

Analytic statements are statements that are true by definition. Examples of analytic statements include the statement "All bachelors are unmarried" and the statement "2 + 2 = 4".

Synthetic statements are statements that are true in all possible worlds. Examples of synthetic statements include the statement "The sun is a star", the statement "There is life on other planets", the statement "The Earth is round", and the statement "Humans are mortal".

Necessary truths are statements that are true in all possible worlds. Contingent truths are statements that are not true in all possible worlds.

Necessary truths are statements that are true in all possible worlds. Examples of necessary truths include the laws of logic and the fact that 2 + 2 = 4.

Contingent truths are statements that are not true in all possible worlds. Examples of contingent truths include the fact that the Earth is round, the fact that there is life on other planets, and the fact that humans are mortal.

A priori necessities are necessary truths that are known to be true without the need for experience. A posteriori necessities are necessary truths that are acquired through experience.

A priori necessities are necessary truths that are known to be true without the need for experience. Examples of a priori necessities include the laws of logic and the fact that 2 + 2 = 4.

A posteriori necessities are necessary truths that are acquired through experience. Examples of a posteriori necessities include the fact that the Earth is round, the fact that there is life on other planets, and the fact that humans are mortal.