"I wait with some impatience for a second edition, principally on account of alterations I intend to make in my performance. This is an advantage that we authors possess since the invention of printing, and renders the _nonum prematur in annum_ not so necessary to us as to the ancients. Without it I should have been guilty of a very great temerity, to publish at my years so many novelties in so delicate a part of philosophy; and at any rate, I am afraid that I must plead as my excuse that very circumstance of youth which may be urged against me. I assure you, that without running any of the heights of scepticism, I am apt in a cool hour to suspect, in general, that most of my reasonings will be more useful by furnishing hints and exciting people's curiosity, than as containing any principles that will augment the stock of knowledge, that must pass to future ages.[118:1] I wish I could discover more fully the particulars wherein I have failed. I admire so much the candour I have observed in Mr. Locke, yourself, and a very few more, that I would be extremely ambitious of imitating it, by frankly confessing my errors. If I do not imitate it, it must proceed neither from my being free from errors nor want of inclination, but from my real unaffected ignorance. I shall consider more carefully all the particulars you mention to me: though with regard to _abstract ideas_, 'tis with difficulty I can entertain a doubt on that head, notwithstanding your authority. Our conversation together has furnished me a hint, with which I shall augment the second edition. 'Tis this--the word _simple idea_ is an abstract term, comprehending different individuals that are similar. Yet the point of their similarity, from the very nature of such ideas, is not distinct nor separable from the rest. Is not this a proof, among many others, that there may be a similarity without any possible separation even in thought. "I must consult you in a point of prudence. I have concluded a reasoning with these two sentences: 'When you pronounce any action or character to be vicious, you mean nothing but that, from the particular constitution of your nature, you have a feeling or sentiment of blame from the contemplation of it. Vice and virtue, therefore, may be compared to sounds, colours, heat, and cold, which, according to modern philosophy, are not qualities in objects, but perceptions in the mind. And this discovery in morals, like that other in physics, is to be regarded as a mighty advancement of the speculative sciences, though like that too it has little or no influence on practice.'[119:1]