Nothing can be conceived more hard than the heart of a thorough-bred metaphysician. It comes nearer to the cold malignity of a wicked spirit than to the frailty and passion of a man. It is like that of the Principle of Evil himself, incorporeal, pure, unmixed, dephlegmated, defecated evil! It is no easy operation to eradicate humanity from the human breast. What Shakspeare calls the compunctious visitings of Nature will sometimes knock at their hearts, and protest against their murderous speculations. But they have a means of compounding with their nature. Their humanity is not dissolved; they only give it a long prorogation. They are ready to declare that they do not think two thousand years too long a period for the good that they pursue. It is remarkable that they never see any way to their projected good but by the road of some evil. Their imagination is not fatigued with the contemplation of human suffering through the wild waste of centuries added to centuries of misery and desolation. Their humanity is at their horizon,and, like the horizon, it always flies before them. The geometricians and the chemists bring, the one from the dry bones of their diagrams, and the other from the soot of their furnaces, dispositions that make them worse than indifferent about those feelings and habitudes which are the supports of the moral world. Ambition is come upon them suddenly; they are intoxicated with it, and it has rendered them fearless of the danger which may thence arise to others or to themselves. These philosophers consider men in their experiments no more than they do mice in air-pumps or in a recipient of mephitic gas. Whatever his Grace may think of himself, they look upon him, and everything that belongs to him, with no more regard than they do upon the whiskers of that little long-tailed animal that has long been the game of the grave, demure, insidious, spring-nailed, velvet-pawed, green-eyed philosophers, whether going upon two legs or upon four.
Edmund Burke: Letter to a Noble Lord upon the Attacks upon his Pension, 1796.
The science of the mathematics performs more than it promises, but the science of metaphysics promises more than it performs. The study of the mathematics, like the Nile, begins in minuteness but ends in magnificence; but the study of metaphysics begins with a torrent of tropes, and a copious current of words, yet loses itself at last in obscurity and conjecture, like the Niger in his barren deserts of sand.
Metaphysical inquiry attempts to trace things to the very first stage in which they can, even to the most penetrating intelligences, be the subjects of a thought, a doubt, or a proposition; that profoundest abstraction, where they stand on the first step of distinction from nonentity, and where that one question might be put concerning them, the answer to which would leave no further question possible. And having thus abstracted and penetrated to the state of pure entity, the speculation would come back, tracing it into all its modes and relations; till at last metaphysical truth, approaching nearer and nearer to the sphere of our immediate knowledge, terminates on the confines of distinct sciences and obvious realities. Now, it would seem evident that this inquiry into primary truth must surpass, in point of dignity, all other speculations. If any man could carry his discoveries as far, and make his proofs as strong, in the metaphysical world, as Newton did in the physical, he would be an incomparably greater man than even Newton.
John Foster: Life and Thoughts, by W. W. Everts, 295.
When the inductive and experimental philosophy recommended by Bacon had, in the hands of Boyle and Newton, led to such brilliant discoveries in the investigation of matter, an attempt was soon made to transfer the same method of proceeding to the mind.
Hobbes, a man justly infamous for his impiety, but of extraordinary penetration, first set the example; which was not long after followed by Locke, who was more indebted to his predecessor than he had the candour to acknowledge. His celebrated Essay has been generally considered as the established code of metaphysics.
The fame of Locke is visibly on the decline; the speculations of Malebranche are scarcely heard of in France; and Kant, the greatest metaphysical name on the continent, sways a doubtful sceptre amidst a host of opponents.
[This] is commonly, in the schools, called metaphysics, as being part of the philosophy of Aristotle, which hath that for title; but it is in another sense; for there it signifieth as much as books written or placed after his natural philosophy. But the schools take them for books of supernatural philosophy; for the word metaphysic will bear both these senses.
All the great enigmas which perplex the natural theologian are the same in all ages. The ingenuity of a people just emerging from barbarism is quite sufficient to propound them. The genius of Locke or Clarke is quite unable to solve them. It is a mistake to imagine that subtle speculations touching the Divine attributes, the origin of evil, the necessity of human actions, the foundation of moral obligation, imply any high degree of intellectual culture. Such speculations, on the contrary, are in a peculiar manner the delight of intelligent children and of half-civilized men. The number of boys is not small who, at fourteen, have thought enough on these questions to be fully entitled to the praise which Voltaire gives to Zadig: Il en savait ce quon en a su dans tous les âges; cest-à-dire, fort peu de chose. The book of Job shows that long before letters and arts were known to Ionia these vexing questions were debated with no common skill and eloquence under the tents of the Idumean Emirs; nor has human reason in the course of three thousand years discovered any satisfactory solution of the riddles which perplexed Eliphaz and Zophar.
Lord Thomas Babington Macaulay: Rankes History of the Popes, Oct. 1840.