XLVII. I agree, that our assent to the existence of a thing, should not be extended so far, as not to be confined within less bounds, than the immense space of possibility; letting our belief be regulated by probability, is much safer, than letting it extend to possibilities; possibility, can only be measured by the extent of the divine power; probability, may be guided and limited by the force and credibility of testification. Thus he would act prudently, who with respect to the history of the child of Lubec, should reject a good portion of the circumstances, but still admit enough of them, to render the story a most wonderful one, the like of which, had never been known in former ages; as it is not probable, that the authors who were the countrymen of the child, should lie exorbitantly, in a case where if they had deviated greatly from the truth, it was in the power of thousands of living witnesses to have convicted them of the imposture. XLVIII. From the beforementioned examples, and an infinite number of others that might be instanced, may be inferred, the enormous difference there is between some souls and others, which difference, is owing solely to a difference of temperament; compared to which, that produced by a disparity of age, is very small, even if we compute it from early manhood, to the period of decadence. The result of my own observation, with the exception of here and there a rare instance, is, that those who at thirty years old are dull, will always be dull; that those who at that age are imprudent, will always be imprudent; and that those who at thirty, in matters of argument or conversation, do not talk pertinently, or reason well, will never reason well. I do not however deny, that cultivation will not improve both men and plants, but it will never make thorns bear grapes, or brambles figs.