You have to take science to date into account. If you do not, you will be proven wrong immediately. You will say 'I think the universe is composed entirely of jelly beans', and I will say 'y experiment disproves that'. If there is an empirical way to answer a question, you should use it. Empiricism works well because it is very convincing.
A lot of the time, you do not have an empirical way to answer your question, because the technology doesn't exist, or the terminology for the question that you want to ask doesn't exist, or you haven't yet adequately specified what the question is.
At its best, it should be the building of a rational, informed, theory about a conceivable hypothetical situation, and rational explorations of the implications of that hypothetical.
Even more recently, the entire field of psychology grew directly out of philosophical speculation about mental states. Starting with Kant in the late 18th century and ending with James early in the 20th, the study of the mind became an accepted part of natural philosophy or science (having James on the faculty of Harvard certainly didn't hinder the acceptance of psychology as a science).
One of the things which philosophy does (and has done) is to clarify which questions to ask, how to ask them, and so forth. Once the problem domain is clarified enough, science can step in and start being useful. Of course, there is no clear-cut border between the two (which can be seen historically in the development of physics, biology, etc.)
That's definitely not the only thing which philosophy does, but I think that's the idea being discussed here.