Because everything we know revolves around a series of assumptions apriori: Things like laws of physics, fields, assumptions about foundational asthmatic. There are things that are true simple because they appear to be the most reasonable explanations for what we observe. Even though our methods do not appear to be perfect they have repeatedly delivered the most reasonable and logical explanations for our observations for centuries and thus demand the benefit of the doubt in the continued use.
The only way this could be challenged is if there was a system of logic superior to the one we currently have today, which, is completely possible, so, if you have a methodology of logic greater than what we currently have, or, a scientific methodology better than the methodology we currently have then explain it….
It's kind of like democracy: It isn't perfect but it's the best we have.