If all experiential reasonings depend on the idea of causality, and this has no other support than subjective mental habit, it follows that all knowledge of nature which goes beyond mere observed fact is not knowledge (neither demonstrative knowledge nor knowledge of fact), but belief.[1] The probability of our belief in the regularity of natural phenomena increases, indeed, with every new verification of the assumptions based thereon; but, as has been shown, it never rises to absolute certainty. Nevertheless inferences from experience are trustworthy and entirely sufficient for practical life, and the aim of the above skeptical deliverances was not to shake belief--only a fool or a lunatic can doubt in earnest the immutability of nature--but only to make it clear that it is mere belief, and not, as hitherto held, demonstrative or factual knowledge. Our doubt is intended to define the boundary between knowledge and belief, and to destroy that absolute confidence which is a hindrance rather than a help to investigation. We should recognize it as a wise provision of nature that the regulation of our thoughts and the belief in the objective validity of our anticipation of future events have not been confided to the weak, inconstant, inert, and fallacious reason, but to a powerful instinct. In life and action we are governed by this natural impulse, in spite of all the scruples of the skeptical reason. [Footnote 1: Hume distinguishes belief as a form of knowledge from religious faith, both in fact and in name. In the _Treatise_--the passage is wanting in the _Enquiry_--our conviction of the external existence of the objects of perception is also ascribed to the former, which later formed Jacobi's point of departure. Religious faith is referred to revelation.]