23. What has been said of the child, may be proved true also of adults, however clear and perfect their intellect. If not initiated into questions of philosophy, they will give very nearly the same answers to difficulties proposed on the same matters, and even upon many others more exposed to doubt. Experience proves better than all ratiocination that no one acquires certainty by reflex acts. 24. Philosophers teach that the sources of certainty are the internal sense or consciousness of acts, the external senses, common sense, reason, and authority. A few examples will show us that there is reflection in all these, and how most men, and even philosophers, when they act like men and not like philosophers, think. 25. Suppose a clear-headed person, one however who is ignorant of the questions of certainty, has just seen some monument, the _Escurial_ for instance, which leaves a lively and lasting impression on his mind, and while he recollects his gratification on seeing it, try to make him doubt the existence of this recollection in his mind, and its correspondence as well with the act of seeing as with the edifice itself, and he will very certainly think you are in jest, or will be astounded, and will suspect you of being out of your senses. He discovers no difference between things different as are the actual existence of his recollection, its correspondence with the past act of seeing, and the agreement of both with the edifice seen. He knows in this case no more than a child of six years: "I recollect it, I saw it, it is as I recollect it." This is all his science: he neither reflects, nor separates; all is direct and simultaneous. No matter what suppositions you make, you can never get from the majority of men any better account of the phenomena of the internal sense, than you got from the supposed individual's recollection of the _Escurial_: "all that I know is that it is so." There are here no reflex acts; certainty attends the direct act, and no philosophical considerations can add one iota to the security given by the very force of things, and the instinct of nature. 26. Example of the testimony of the senses.