Dr. Priestley states in his ‘Illustrations’ and in his letter to Dr. Horsley, that the difference between physical and moral necessity is merely verbal. He says, speaking of the connexion between cause and effect in the mind, ‘Give me the thing and I will readily give up the name.’ It appears to me that Dr. Priestley was quite as much attached to the name as to the thing, and that the philosophical principle of necessity, without its unpopular title, would have afforded him but little satisfaction. Now the obnoxiousness of the name, and in my opinion, almost all the difficulty and repugnance which the generality of men find in admitting the doctrine arises from the ambiguity lurking under the term necessity, which includes both kinds of necessity, moral and physical, and with which Dr. Priestley delights to probe the prejudices of his adversaries, thinking the differences of moral and physical necessity a mere question of words, and that provided there are any laws or any causes operating upon the mind, it is of no sort of consequence what those laws or causes are. It is the same inability to distinguish between one cause and another which creates the vulgar prejudice against necessity, and which is exposed in a very satisfactory manner by the author of the ‘Inquiry into the Will.’ He says, in a letter written expressly to vindicate himself from having confounded moral with physical necessity, ‘On the contrary, I have largely declared that the connexion between antecedent things and consequent ones which takes place with regard to the acts of men’s wills, which is called moral necessity, is called by the name of _necessity_ improperly; and that all such terms as _must_, _cannot_, _impossible_, _unable_, _irresistible_, _unavoidable_, _invincible_, &c. when applied here, are not applied in their proper signification, and are either used nonsensically, and with perfect insignificance, or in a sense quite diverse from their original and proper meaning, and their use in common speech; and that such a necessity as attends the acts of men’s wills, is more properly called _certainty_ than _necessity_. I think it is evidently owing to a strong prejudice in persons’ minds, arising from an insensible habitual perversion and misapplication of such-like terms, that they are ready to think that to suppose a certain connexion of men’s volitions without any foregoing motives or inclinations, is truly and properly to suppose such a strong irrefragable chain of causes and effects as stands in the way of, and makes utterly vain, opposite desires and endeavours, like immovable and impenetrable mountains of brass; and impedes our liberty like walls of adamant, gates of brass, and bars of iron: whereas all such representations suggest ideas as far from the truth, as the East is from the West. I know it is in vain to endeavour to make some persons believe this, or at least fully and steadily to believe it: for if it be demonstrated to them, still the old