'One fire burns out another's burning'-- 'One desperate grief cures with another's languish'-- 'Take thou some new infection to thine eye, And the rank poison of the old will die.' _Romeo and Juliet_. 'As fire drives out fire, so pity, pity; And pity to the _general wrong of Rome_ Hath, done this deed _on Cæsar.' _Julius Cæsar_. for it is the _larger_ form, which is the worthier, in that new department of mixed mathematics which this philosopher was cultivating. 'One fire drives out one fire, one nail one nail: Rights by rights fouler, strength by strengths do fail.' _Coriolanus_. And for history of _cases_, see the same author in Hamlet and other plays. [This philosopher's prose not unfrequently contains the key of the poetic paraphrase; and the true reading of the line, which has occasioned so much perplexity to the critics, may, perhaps, be suggested by this connection--'to set affection against affection, and to master one by another, even as we hunt beast with beast, and fly bird with bird.'] CHAPTER V. THE SCIENCE OF MORALITY.--ALTERATION. Hast thou not learn'd me how To make perfumes? distil? preserve? yea, so, That our great king himself doth woo me oft For my confections? Having thus far proceeded, (Unless thou think'st me devilish,) is't not meet That I did amplify my judgment in Other conclusions? _Cymbeline_. Thus far, it is the science of Man, _as he is_, that is propounded. It is a scientific history of the Mind and its diseases, built up from particulars, as other scientific histories are; and having disposed, in this general manner, of that which must be dealt with by way of _application_, those points of nature and fortune, which he puts down as the basis and conditions to _which all our_ WORK _is limited and tied_, we come now to that which IS within our power--to those points which we can deal with by way of ALTERATION, and not of _application_ merely; and yet points which are operating perpetually on the human character, changing the will and appetite, and altering the conduct, by laws not less sure than those which operate in the occult processes of nature, and determine differences behind the scene, or out of the range of our volition.