If it is allowed that the improvements in physic have an influence on the duration of human life, and that these improvements may go on indefinitely, I do not think Mr. Malthus’s answer a conclusive one that no considerable progress will ever be made in this respect, because none has hitherto been made. If the improvements in science have not hitherto been regular and permanent, it cannot be expected that any advantages depending on them should have been so: nor does the past history of mankind in this instance furnish a rule for our future conjectures, inasmuch as in all that relates to the permanence and general diffusion of knowledge, a new turn has been given to the question (as before observed) by the invention of printing. This single circumstance, which was matter of mere accident, may be said in many respects to have given a new aspect to human affairs; to say that it has not yet produced the effects predicted from it, when it has had no time to produce them, is like saying, that the repeated blows of a battering-ram will not break down a stone-wall, because for the two or three first blows it does not begin to move. The true question is, whether the cause is adequate to the effect ascribed to it, that is, whether its operation is of a sufficiently general and powerful nature to produce a correspondent general change in the circumstances of mankind. I think it will hardly be denied that printing may be applied with great success as an instrument for the propagation of vice: may it not then be made use of to give currency to the principles of virtue? At any rate, to deny that it is a means of diffusing and embodying knowledge is to deny that such a contrivance exists at all, or that books will be more generally read, or less liable to be lost from the facility with which they are multiplied. While therefore Mr. Malthus allows certain moral habits, and the state of physical knowledge in a great measure to determine the length of human life, he cannot object on any allowed principles of philosophy to M. Condorcet’s employing these causes as intermediate links in a chain of argument to establish the probability of the gradual approach of mankind—to a state of immortality. The error does not lie in M. Condorcet’s general principles of reasoning, but in the wrong application of them; though I do not know that I could detect the error better than Mr. Malthus has done. What I have endeavoured to shew in these hasty remarks is that the admission of the rule laid down by our author, that in our calculations of the future, we are to attend to nothing but the general state of the fact hitherto, without giving any weight to the actual change of collateral circumstances, or the existence of any new cause which may influence the state of that fact, would overturn every principle, not only of sound philosophy, but of the most obvious common sense.[27] I dissent equally from M. Condorcet’s paradoxical speculations and from Mr.