For an example, choose any point of history, and consider why we either believe or reject it. Thus, we believe that Caesar was killed in the senate-house on the ides of March, because this is established on the unanimous testimony of historians, who agree in assigning this precise time and place to that event. Here are certain words that we see or remember, words that we remember to have been used as the signs of certain ideas; and these ideas—·the ones in the minds of writers of the history books·—were those of people who •were immediately present at assassination and received their ideas directly from it, or who •got their ideas from the testimony of others, who relied on yet earlier testimony, and so on backwards until the slope stops at those who saw the assassination. It is obvious that all this chain of argument or connection of causes and effects is initially based on words that are seen or remembered, and that without the authority of either the memory or senses our whole reasoning would be chimerical and without foundation: every link of the chain would hang on another; but there would be nothing fixed to one end of it that could support the whole chain, and so there would be no belief. And this is actually the case with all hypothetical arguments, or reasonings from a supposition, for in them there is no present impression and no belief about a matter of fact.