That is what I used to think, but if you dig a little deeper I'm not sure it's quite that simple. If you read the link I posted, all that work on alchemy was not printed after his death because people examined it and deemed it "not fit to print". So it definitely seems that even at the time, there may not have been a clear line, but people felt that his alchemical writings were on the wrong side of whatever line might in future be drawn.

Newton was also definitely in favour of an empirical/axiomatic basis for science in general. If you read principia he proves almost everything[1] and of course he famously deformed his own eyeballs with wooden gadgets to do his experiments in optics.

[1] In fact pretty much the one thing he doesn't prove is the calculus, which Alex Kontorovich once said in a lecture on youtube that he has a pet theory that the reason that Newton never published the calculus was not the one everyone says about his rivalry with Hooke etc but that he wanted a rigorous proof first (which of course didn't come about until much later with Cauchy, Weierstrass, Dedekind etc for normal calculus and the 1960s for non-standard analysis to prove Newton's fluxions rigorously).