A man cannot prove a negative, but he has a right to claim that when a man makes an affirmative charge, he must offer some proof to show the truth of what he says.  I certainly cannot introduce testimony to show the negative about things, but I have a right to claim that if a man says he knows a thing, then he must show how he knows it.  I always have a right to claim this; and it is not satisfactory to me that he may be “conscientious” on the subject.

...  Anything that argues me into his idea of perfect social and political equality with the negro is but a specious and fantastic arrangement of words, by which a man can prove a horse-chestnut to be a chestnut horse.  I will say here, while upon this subject, that I have no purpose, either directly or indirectly, to interfere with the institution of slavery in the States where it exists.  I believe I have no lawful right to do so, and I have no inclination to do so.  I have no purpose to introduce political and social equality between the white and the black races.  There is a physical difference between the two, which, in my judgment, will probably for ever forbid their living together upon the footing of perfect equality; and inasmuch as it becomes a necessity that there must be a difference, I, as well as Judge Douglas, am in favour of the race to which I belong having the superior position.  I have never said anything to the contrary; but I hold, that, notwithstanding all this, there is no reason in the world why the negro is not entitled to all the natural rights enumerated in the Declaration of Independence,—­the right to life, liberty, and the pursuit of happiness.  I hold that he is as much entitled to these as the white man.  I agree with Judge Douglas, he is not my equal in many respects, certainly not in colour, perhaps not in moral or intellectual endowment.  But in the right to eat the bread, without the leave of anybody, which his own hand earns, he is my equal, and the equal of Judge Douglas, and the equal of any living man.

...  As I have not used up so much of my time as I had supposed, I will dwell a little longer upon one or two of these minor topics upon which the Judge has spoken.  He has read from my speech at Springfield, in which I say that “a house divided against itself cannot stand.”  Does the Judge say it can stand?  I don’t know whether he does or not.  The Judge does not seem to be attending to me just now, but I would like to know if it is his opinion that a house divided against itself can stand?  If he does, then there is a question of veracity, not between him and me, but between the Judge and an authority of a somewhat higher character.