"The Approach to Metaphysics"
Charles Sanders Peirce (1898-1903)
(From Philosophical writings of Peirce, selected and edited with an introduction by Justus Buchler (New York: Dover Publications, 1955)

"...The common opinion has been that Metaphysics is backward because it is intrinsically beyond the reach of human cognition. That that, I think I can clearly discern, is a complete mistake. Why should metaphysics be so difficult? Because it is abstract? But the [more abstract] a science is, the easier it is, both as a general rule of experience and as a corollary from logical principles. Mathematics, which is far more abstract than metaphysics, is certainly more developed than any special science; and the same is true, though less tremendously so, of logic. But it will be said that metaphysics is inscrutable because its objects are not open to observation. This is doubless true of some systems of metaphysics, though not to the extent that it is supposed to be true. The things that any science discovers are beyond the reach of direct observation [emphasis added]. We cannot see energy, nor the attraction of gravitation, nor
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the flying molecules of gases, nor the luminiferous either, nor the forests of the carbonaceous era, nor the explosions in nerve-cells. It is only the premises of science, not its conclusions, which are directly observed emphasis added]. But metaphysics, even bad metaphysics, really rests on observations, whether consciously or not; and the only reason that this is not universally recognized is that it rests upon kinds of phenomena with which every man's experience is so saturated that he usually pays not particular attention to them. The data of metaphysics are not less open to observation, but immeasurably more so, than the data, say, of the very highly developed science of astronomy [emphasis added], to make any important addition to whose observation requires and expenditure of many tens of thousands of dollars. No, I think we must abandon the idea that metaphysics is backward owing to any intrinsic difficulty of it.
  In my opinion the chief cause of its backward condition is that its leading professors have been theologians [emphasis added]. ...

... But the idea of science is to pile the ground before the foot of the outworks of truth with the carcasses of this generation, and perhaps of others to come after it, until some future generation, by treading on them, can storm the citadel. The difference comes to this, that the
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practical man stakes everything he cares for upon the hazard of a die, and must believe with all the force of his manhood that the object for which he strives is good and that the theory of his plan is correct; while the scientific man is above all things desirous of learning the truth and, in order to do so, ardently desires to have his present provisional beliefs (and all his beliefs are merely provisional) swept away, and will work hard to accomplish that object [emphasis added]. This is the reason that a good practical man cannot do the best scientific work. The temperaments requisite for the two kinds of business are altogether contrary to one another. This is above all true of the practical teacher [who] has no calling for this work unless he thorougly believes that he is aleady in possession of all-important truth, with which he seeks by every physiological means to imbue other minds, so that they shall be unable to give it up. But a scientific man, who has any such immovable beliefs to which he regards himself as religiously bound to be loyal, cannot at the same time wish to learn the truth. Hence, I say that had the business of metaphysics been entrusted to ordinary parish priests it would have been performed unscientifically enough. But what has in fact been its fate has been far more tragic, in that it has been given over not to parish priests but to the caste of theologians. How much theologians may have contributed to the cause of Christianity, how far their writings and performances may have [been] the instruments of bringing home to men's hearts the truth of the Gospel of Love, or how far, on the other hand, they may have subserved the agencies that work to make Christians forget that truth, it is not in my province to inquire. I once bought and read through Dr. Schaff's three volumes upon the Creeds of Christendom for the purpose of ascertaining whether the theologians, who composed them, had ever once, from first to last, inserted a single clause in one of them by way of recognition of the principle of love; and I found that such a thing had never been done. But then we must remember that, the principle being fully admitted by all Christians, its insertion would not have served to damn anybody. Now the principle business of theologians is to make men feel the enormity of the slightest departure from the metaphysics they assume to be connected with the standard faith. Upon their religious side, however, I will not pretend to any opinion about the influence of theologians. But since theology pretends to be a science, they must also be judged as scientific men. And in that regard I must say that another so deplorably corrupt an influence as theirs upon the morals
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of science I not believe has ever been operative. Theology, I am persuaded, derives its initial impulse from a religious wavering; for there is quite as much, or more, that is mysterious and calculated to awaken scientific curiosity in the intercourse of men with one another as in their intercourse with God
[emphasis], and it [is] a problem quite analogous to that of theology. Yet we do not find that theologians have cared much for those problems. They have taken human conversation as a matter of course, with rather a remarkable absence of all curiosity about it. But, as far as I can penetrate into the motive of theology, it begins in an effort of men who have joined the Christian army and sworn fidelity to it to silence the suggestions of their hearts that they renounce their allegiance. How far it is successful in that purpose I will not inquire. But nothing can be more unscientific than the attitude of minds who are trying to confirm themselves in early beliefs. The struggle of the scientific man is to try to see the errors of his beliefs — if he can be said to have any beliefs. The logic which observational science uses is not like the logic that the books teach, quite independent of the motive and spirit of the reasoner. There is an ethics indissolubly bound up with it — an ehtics of fairness and impartiality — and a writer, who teaches, by his example, to find arguments for a conclusion which he wishes to believe, saps the very foundations of science by trifling with its morals [emphasis added].