I consider philosophy to be essential in knowing truth, so here I define and describe what I think philosophy is, and why it matters.

Philosophy includes these aspects:

  1. Epistemology — knowledge, truth, certainty, belief.
  2. Logic and mathematics — sound reasoning, arguments.
  3. Natural science (also called: physics, natural philosophy, experimental philosophy). Note that science is a part of philosophy.
  4. Social science — economics, history, political science, psychology, sociology, anthropology, archaeology.
  5. Metaphysics — reality, mind and matter.
  6. Ontology — being.
  7. Ethics — morality, right and wrong, good and evil.
  8. Aesthetics — beauty, art.
  9. Politics — social interactions, power, government, law.

The difference between science and philosophy:

  1. When you have good data, sufficient data; it's called science. (Using the scientific method with repeatable experiments or able to make predictions, and must be falsifiable.)
  2. Otherwise, it's called philosophy. (Examples: (1) proposing a scientific hypothesis, (2) assessing a historical event with insufficient or ambiguous documents and artifacts, (3) rejecting numerology, (4) game theory.)

All knowledge is based on probability, meaning, we can never be 100% certain of anything. The question is: what probability threshold should we require to believe something as true?

Believing something provably untrue is called delusion. A good example is believing in a flat earth. Many conspiracy theories are based on delusions.

Facts correspond to reality. In constructing logical arguments, we should use facts. Otherwise our conclusions will be flawed or false.

We should believe things that are true, and not believe things that are false.

The mind is prone to error, to cognitive bias. Before believing something, it's important to first try diligently to prove it false, but in the end to fail. And also: consider whether the evidence also supports views other than the one you wish to believe — are there alternate explanations for the data?