On the Improvement of Understanding, by Benedict de Spinoza, [1883], at sacred-texts.com
[43] (1) It may, perhaps, provoke astonishment that, after having said that the good method is that which teaches us to direct our mind according to the standard of the given true idea, we should prove our point by reasoning, which would seem to indicate that it is not self-evident. (2) We may, therefore, be questioned as to the validity of our reasoning. (3) If our reasoning be sound, we must take as a starting-point a true idea. (4) Now, to be certain that our starting-point is really a true idea, we need proof. (5) This first course of reasoning must be supported by a second, the second by a third, and so on to infinity.
[44] (1) To this I make answer that, if by some happy chance anyone had adopted this method in his investigations of nature—that is, if he had acquired new ideas in the proper order, according to the standard of the original true idea, he would never have doubted [q] of the truth of his knowledge, inasmuch as truth, as we have shown, makes itself manifest, and all things would flow, as it were, spontaneously towards him. (44:2) But as this never, or rarely, happens, I have been forced so to arrange my proceedings, that we may acquire by reflection and forethought what we cannot acquire by chance, and that it may at the same time appear that, for proving the truth, and for valid reasoning, we need no other means than the truth and valid reasoning themselves: for by valid reasoning I have established valid reasoning, and, in like measure, I seek still to establish it.
[45] (1) Moreover, this is the order of thinking adopted by men in their inward meditations. (2) The reasons for its rare employment in investigations of nature are to be found in current misconceptions, whereof we shall examine the causes hereafter in our philosophy. (3) Moreover, it demands, as we shall show, a keen and accurate discernment. (4) Lastly, it is hindered by the conditions of human life, which are, as we have already pointed out, extremely changeable. (5) There are also other obstacles, which we will not here inquire into.
[46] (1) If anyone asks why I have not at the starting-point set forth all the truths of nature in their due order, inasmuch as truth is self-evident, I reply by warning him not to reject as false any paradoxes he may find here, but to take the trouble to reflect on the chain of reasoning by which they are supported; he will then be no longer in doubt that we have attained to the truth. (2) This is why I have as above.
[47] (1) If there yet remains some sceptic, who doubts of our primary truth, and of all deductions we make, taking such truth as our standard, he must either be arguing in bad faith, or we must confess that there are men in complete mental blindness either innate or due to misconceptions—that is, to some external influence. (2) Such persons are not conscious of themselves. (3) If they affirm or doubt anything, they know not that they affirm or doubt: they say that they know nothing, and they say that they are ignorant of the very fact of their knowing nothing. (4) Even this they do not affirm absolutely, they are afraid of confessing that they exist, so long as they know nothing; in fact, they ought to remain dumb, for fear of haply supposing which should smack of truth.
[48] (1) Lastly, with such persons, one should not speak of sciences: for, in what relates to life and conduct, they are compelled by necessity to suppose that they exist, and seek their own advantage, and often affirm and deny, even with an oath. (2) If they deny, grant, or gainsay, they know not that they deny, grant, or gainsay, so that they ought to be regarded as automata, utterly devoid of intelligence.
[49] (1) Let us now return to our proposition. (2) Up to the present, we have, first, defined the end to which we desire to direct all our thoughts; secondly, we have determined the mode of perception best adapted to aid us in attaining our perfection; thirdly, we have discovered the way which our mind should take, in order to make a good beginning—namely, that it should use every true idea as a standard in pursuing its inquiries according to fixed rules. (49:3) Now, in order that it may thus proceed, our method must furnish us, first, with a means of distinguishing a true idea from all other perceptions, and enabling the mind to avoid the latter; secondly, with rules for perceiving unknown things according to the standard of the true idea; thirdly, with an order which enables us to avoid useless labor. (49:4) When we became acquainted with this method, we saw that, fourthly, it would be perfect when we had attained to the idea of the absolutely perfect Being. (5) This is an observation which should be made at the outset, in order that we may arrive at the knowledge of such a being more quickly.