One of the fascinating things about doing science actively is that there are always big assumptions which cannot be avoided - the basic way in which the world is carved-up and causally explained. And sometimes it is obvious that all the rest is just measuring and fiddling, in comparison.
But the presumption is that these big assumptions will, sooner or later, get dealt-with, and placed on a secure footing. But it almost never happens - yet science goes-on.
So biology never really sorts-out what is a gene, an organism, a species - but uses rough and ready definitions and explains 'about' these things.
Karl Popper noticed this many years ago - that at the heart of an active science are vague definitions - and that strict and precise definitions will kill science.
It is possible that this is intrinsic to real science, but also one of the major factors that makes science into something which is not formally interpretable or applicable.
There is always a huge leap of faith in using science in the rest of the world; as there is in applying mathematics to concrete objects. And no formal mechanism of finding out whether science necessarily will work, is working, or has worked.
NOTE ADDED: What this implies is that science is not independent of the striving for truth - but always needs to be conducted in a spirit of the love of truth; a truth that goes beyond any specific science, beyond science as a whole, beyond philosophy and is indeed transcendant.
The products of science need to be tested in accordance with Truth.
When science worked it was indeed conducted in such as spirit - since this spirit has been disappearing, so science has dwindled into bureaucracy and careerism.