A slice of philosophy

After reading an anthology on (selected) philosophers starting with Aristotle, I feel that not much that would offer an explanation to questions like What is life? or Why are we here?, but an awful lot of mumbo jumbo, has been written since the days of Thomas of Aquino.
(He, at least, gave suggestions how to try and prove the existence of God; he pointed to the movement of things, and the laws of cause and effect, among other things.)

It is true, though, that a number of interesting thoughts have emerged during this span of time. But they have mainly focused on how not to answer the big questions; many thinkers seem to concentrate on how to declare invalid the theories of their opponents.
For example did the school of logic positivism state that metaphysics isn't something that explains facts, but only belief. And Karl Popper, in an essay on the brilliance of Einstein, noted that the most scientific method is the critical one - where you go to great lengths, not trying to verify a theory but to confute it.

Another interesting question is: What is philosophy? Where does it start? Who is a philosopher?
Maybe my grocer is a great philosopher when he says that one should not worry about things one cannot have an influence on.

Would I be considered a philosopher if I publish these thoughts:
How can we identify something as the truth?
For example, if I am standing in front of something I would like to call a tree, and my friend, who is standing next to me, agrees that this is a tree, can we then be sure that it really is a tree? Is it then the truth that it is a tree?
And how long would this be the truth?
What if a third person came up to us and said that it is not a tree, it's a bush. Will "our" truth then cease to be the truth?