Best for last. (I wish I could explain all of this more in depth but I was only a philosophy minor. Very passionate about this though.)
  1. Thales
    Everything is water. He observed all life needs water and concluded that therefore water was the main component of all of life. Everything could be traced back to water etc etc
  2. Heraclitus
    Said that everything is actually fire, not water. Also said you can't step in the same river twice.
  3. Parmenides
    "The same is for thinking and for being." Meaning, if it can be comprehended by intellect, it can exist. In order for a thing to BE it must be able to be grasped by intellect.
  4. Aristotle
    He had similar thoughts to Plato but thought that a thing has to exist before the idea can exist. That's the opposite of plato's main philosophy. Learned from Plato, though. He's very important for his poetics and other logical philosophies he came up with but I didn't study those as much.
  5. Plato
    The forms, the cave. For something to exist the form/idea/Eidos (see tattoo below my right rib) must exist first. Before there is a chair there has to be chairness. The forms/Eidos are real and what we see are just shadows of the real (aka really real reality). Allegory of cave: humans are living in a cave looking and shadows of puppets. The puppets represent reality and the shadows represent the images WE experience, which are only material manifestations of reality, I.e the forms.
  6. Plotinus
    All existence derives from the One, also known as the unmoved mover. Responsible for all things and so it itself cannot be a thing. Cannot be a thing or an it, cannot be grasped by human intellect.
  7. I could go on for literally ten years. Stopping now.