I am better able to enter into the character of this description of men than the noble Duke can be.  I have lived long and variously in the world.  Without any considerable pretensions to literature in myself, I have aspired to the love of letters.  I have lived for a great many years in habitudes with those who professed them.  I can form a tolerable estimate of what is likely to happen from a character chiefly dependent for fame and fortune on knowledge and talent, as well in its morbid and perverted state as in that which is sound and natural.  Naturally, men so formed and finished are the first gifts of Providence to the world.  But when they have once thrown off the fear of God, which was in all ages too often the case, and the fear of man, which is now the case, and when in that state they come to understand one another, and to act in corps, a more dreadful calamity cannot arise out of hell to scourge mankind.  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 from thence arise to others or to themselves.  These philosophers consider men in their experiments no more than they do mice in an air-pump 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 been long the game of the grave, demure, insidious, spring-nailed, velvet-pawed, green-eyed philosophers, whether going upon two legs or upon four.