Please correct me if I´m wrong, but if, as epepke wrote, when building a philosophy one "start from assumptions or basic principles, assign truth values to them, and build up using some forms of logic", wouldn´t it be the correct next step to test it against avaliable information, that usually comes from science?
Well, you're not
wrong as such, but you're not exactly right either. The exact methodology of philosophy is as much a subject of philosophy as anything else in the discipline, in fact, and there are plenty of reasons to consider that construal to be a very iffy one. (For instance, what you've described sounds like a good way to do formal logic, but it's highly questionable when it comes to ethics.) Recourse to intuitions in various cases is an important part of philosophy, but it's also a highly dangerous one since intuitions are only, well, intuitions....
Is this is so, I guess it would be correct to state that science is a base to a philosophy (at least nowdays). On the other hand, consider a philosophy that does not do so, remaining untested....
While it's fair to say that any philosophic position that makes it impossible to do something that clearly we
are doing has a distinct problem, that's really the only way in which we can speak of science being a basis for philosophy. After all, science must accept a variety of assumptions in order to do anything at all that we would accept as inquiry, and cannot return results that tell against those assumptions (imagine an experiment that falsified the (broadly construed) scientific method). These assumptions and methods, then, are valid subjects of philosophic inquiry. Furthermore, I should note, any scientific theory that fails on philosophic grounds (for instance, contains a contradiction or relies on a critical equivocation in order to return positive results, or that sort of thing) automatically fails as a scientific theory.
The famous chestnut "I think, therefore I am" isn't really a proof of anything. It is a statement of an assumption.
It isn't really either, honestly. "I think" is a statement that cannot be thought without being true, which means that - as doubting is considered a type of thinking - it's a statement that cannot be
doubted (because doubting the statement "I am doubted" would be contradictory). Descartes doesn't start from "I think", rather he concludes that it's something he cannot sensibly doubt (he starts by coming up with a method that involves doubting anything he can doubt, and seeing what constitutes an undoubteable foundation). There are various problems with his method, certainly, but very few people have argued that one can doubt that one is capable of doubting.
Finally, in response to epepke, I think you're making a very odd statement when you say:
Anyway, science is robust in terms of ignorance or uncertainty, whereas most philosophy is rather fragile. A scientific chain of logic where one term is changed from 100% to 99%, or "infinite" versus "really, really big" can still work, while most philosophical positions fall apart if this is so.
Is it reasonable, do you think, to compare science-as-a-whole to any particular philosophic position? After all, any particular scientific hypothesis is pretty fragile - or at least ideally so for testing purposes. If you want to compare various theories which have to stand up to a barrage of experiments designed to falsify them (most of which, again ideally,
do end up falsified) to a various philosophic arguments or theories which have to stand up to a barrage of other arguments designed to disprove them or at the very least provide substantial reason to consider them false (most of which
do end up being rejected), then you're welcome to do that - but that wouldn't exactly give you as substantial a difference any more. I'm not sure why when it comes to science that feature is a positive feature and when applied to philosophy it's a negative one.
Also:
1) Observation that it works, as you mentioned.
2) The idea that the only real test of a hypothesis is observation or experiment
3) Feynman's characterization of science as a "satisfactory philosophy of ignorance"
However, there are a couple of problems. The first is that it is different from those things that are generally approved of by philosophers these days. 1 and 2 are likely to elicit a response of "empiricism is dead, you loser" or maybe "logical positivism is dead, you loser" or something like that.
I should note just from the get go that there
are valid reasons to consider (1) and (2) problematic. A reason (1) might be considered problematic is that evaluating whether or not science "works" involves determining exactly what it means for science to "work" (does it mean converging on truth, or higher predictive power, for instance - and can one of those two strictly be said to imply the other?). Certain views of what it means to say that science works are overly naive, in fact, which shouldn't surprise anyone familliar with, say, the view that science reveals the natural law of the universe as put there by God and blah blah blah....
Secondly, (2) is downright false, because there are plenty of other real tests that we put on hypotheses. As noted above, any hypothesis that blatantly fails to pass philosophic muster is a bad one(try to devise an experiment that would falsify a logical contradiction). Also there are various principles involving parsimony that are not based on any observations as such and which serve as criteria on which to evaluate hypotheses.
Now, none of the things I've said above demonstrate anything
wrong with science, but it is important to remember that it's very easy to take a naive view of things that can be quite misleading at times.
