Metaphysics: In a simple way metaphysics is the study of being. Metaphysical thought contemplates the fundamental nature of how and why things exist. The word is derived from the greek phrase ta meta ta phusika which refers to a work by Aristole (That carries the same name) and quite literally means “the ones after the physical ones.” The title was not given by Aristotle himself, but rather by an editor compiling his writings over a century later. If you remember substance from our earlier discussions, you will recognize that because knowing a substance is to know what it is fundamentally without characteristics, the knowledge of the substance is a metaphysical knowledge (or assertion). When we say we know the computer before us as a computer we are making a metaphysical assertion about what that object before us really is.
Epistemology: Is the study of how we know things. It is derived from two greek words: the verb epistasthai which means “to be known” and the noun logos which is a rich word that means “the thing spoken of”, or “the subject mater of”. We use epistemology to decide the limits and boundaries of what can or cannot be known. When we say that we can know the square root of four but that the square root of two is irrational and thus we cannot truly know it, we are making a Epistemological claim.
Logic: The rules by which we perform philosophy. Logic is the fundamental system by which we study philosophy. It is also derived from the greek word logos but is often attributed to logikos which is the adjectival form. Its function in philosophy is to provide a consistent foundation of principles from which to build from.
Ethics: Is the study of how we are to engage the world. It is related to morals but being abstract, it is distinct from ones particular action and instead attempts to justify objectively the fundamental way in which things ought to consistently interact. It is derived from the greek word ethos which means habit or habitual action. Ethics is used practically to determine the laws and rules from which a society can operate.
Aesthetics: The study of how and why something can be considered objectively “beautiful” and what value we assign to that beauty. It is derived from the adjectival form of the greek verb aisthanomai which means “to be perceived.” Both Ethics and Aesthetics make up what is typically called Axiology (from axios which means value), and is the study of value qua value.