Huh, tell me more ... tell me more of how my knowledge of my existence s less questionable than gravity.
You can define yourself as that which causes your thoughts to appear in your head. Once you've done that, you (and only you) know that you exist as that entity. You don't even know for sure what you are, or your own nature, but you know that you exist as that entity.
The next thing you know is logic, and you don't know this as well as you know you exist. Logic sets up some rules and follows those rules. Logic says something like the following:
Suppose that I knew every time I have an apple I would also have a banana.
Now suppose I had an apple.
It would logically follow that I had a banana.
Now, you don't have to have an apple or a banana for that to be true. Apples and bananas do not need to actually exist in the universe for that to be true. I could substitute marklar for apple and well it would be marklar for banana too. Point is, the universe need not exist or contain an apple for logic to be correct that if you knew that every time you had an apple (even if you never do) you also had a banana (even if bananas are a figment of your imagination), and you knew you had an apple (even if you never do and they're also a figment of your imagination) that you'd also have a banana (whatever that is). Logic is based on deductive reasoning. If you assume a premise, you can deduce a conclusion.
Logic is fairly unquestionable because of its own self-contained premises. Even in the presence of a supernatural being that could change reality in a blink, logic still holds up. Because if God makes that banana disappear once you get an apple, your premises are now wrong. In the presence of a supreme being that can change the laws of nature and blink things into and out of existence though, logic is meaningless (even if still true) - because anything follows from the God premise. And that's why logic is #2 on the list and not co-number 1.
Math is #3 on the list because of the God problem. Math assumes something about the universe, namely that things don't blink into and out of existence, that if you put one thing together with another thing you have two things, and that god doesn't make a third thing pop into existence as soon as you added those two things together. Math is like applied logic, and the moment you apply it you assume something about the nature of reality - which is why it's number 3. If you made math conditional on the axioms that math is based on, then it just becomes a logic experiment and can be co-number 2, but really becomes moot until you assume that those axioms are truth.
Theory is #4 because it is fundamentally based on inductive reasoning (I say fundamentally because you can apply deductive reasoning to reach a conclusion, but you're using induction to apply it to reality). A theory is simply an explanation that fits the available evidence (facts). As new facts are presented, the theory may need to be altered to fit all available facts. This is the flaw in induction, you never know what new facts might be presented. It is easy to be wrong using induction: My apple is red, your apple is red, by induction we can conclude that apples are red (false). Fundamentally this is what science does, but science is aware of it and allows for adjustment to new evidence. Think of this as a "best effort" scenario. Obviously we can't achieve perfect knowledge, but we can draw some conclusions based on what we have seen and perhaps develop something useful. In fact, this method has turned about to remarkably useful.
Theory is where gravity falls into play. Gravity is a theory that fits the available evidence. It fits all available evidence (which is what a good theory does), but all it would take is one new example that doesn't fit our theory of gravity and suddenly it's back to the drawing board - totally possible. Gravity is based on inductive reasoning.
My apple is red, your apple is red, all apples are red (false)
My mass attracts, your mass attracts, all mass attracts (true?)
Hypothesis is #5 because it hasn't been tested against reality.
Perception might be co-number 5 or I might put it at #6 because perception is so easily incorrect - and often we know that it is incorrect because we are very familiar with where our biological perceptions go wrong. Your blind spot is a good example of that. You know that your finger doesn't disappear when you put it in your vision's blind spot, even though you perceive it disappearing.
Depending on one's approach to religion it is either hypothesis or perception.
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