Hard science is a philosophical method based on observation. It only requires the existence of a falsifiable premise (hypothesis) and method of measurement that bears repeatable results. Loosely the term science can refer to any organized knowledge -- e.g., the science of motorcycle maintenance.
Inherent in the idea of scientific measurement is the idea that there exists some quality that is measurable. In other words, we can apply some sort of non arbitrary and fundamental units of measurement to some particular quality of the natural universe -- for example, time, distance, and dispacement.
Science exists because enlightened people figured out that we cannot always trust our senses. They came to the conclusion that there must be some method based in logic that would provide the best gage for judging truths about the natural universe. All sciences must have their derivations in logic.
Logic is the only thing we can trust because logical truth must be consistent with the reason. Logic is nothing more than the science (as in organized knowledge versus an observational method) of rational thinking.
Science does not guarantee truth; it can only guarantee statistically significant results under a completely known set of circumstances.