"Is it not, then, demonstrated that truth is not the object of your contests? that it is not her cause which you defend, but that of your affections, and your prejudices? that it is not the object, as it really is in itself, that you would verify, but the object as you would have it; that is to say, it is not the evidence of the thing that you would enforce, but your own personal opinion, your particular manner of seeing and judging? It is a power that you wish to exercise, an interest that you wish to satisfy, a prerogative that you arrogate to yourself; it is a contest of vanity. Now, as each of you, on comparing himself to every other, finds himself his equal and his fellow, he resists by a feeling of the same right. And your disputes, your combats, your intolerance, are the effect of this right which you deny each other, and of the intimate conviction of your equality. "Now, the only means of establishing harmony is to return to nature, and to take for a guide and regulator the order of things which she has founded; and then your accord will prove this other truth: "That real beings have in themselves an identical, constant and uniform mode of existence; and that there is in your organs a like mode of being affected by them. "But at the same time, by reason of the mobility of these organs as subject to your will, you may conceive different affections, and find yourselves in different relations with the same objects; so that you are to them like a mirror, capable of reflecting them truly as they are, or of distorting and disfiguring them. "Hence it follows, that whenever you perceive objects as they are, you agree among yourselves, and with the objects; and this similitude between your sensations and their manner of existence, is what constitutes their truth with respect to you; and, on the contrary, whenever you differ in opinion, your disagreement is a proof that you do not represent them such as they are,--that you change them. "Hence, also, it follows, that the causes of your disagreement exist not in the objects themselves, but in your minds, in your manner of perceiving or judging. "To establish, therefore, a uniformity of opinion, it is necessary first to establish the certainty, completely verified, that the portraits which the mind forms are perfectly like the originals; that it reflects the objects correctly as they exist. Now, this result cannot be obtained but in those cases where the objects can be brought to the test, and submitted to the examination of the senses. Everything which cannot be brought to this trial is, for that reason alone, impossible to be determined; there exists no rule, no term of comparison, no means of certainty, respecting it.