Huxley helped largely in the modern movement which has made it impossible to blame people for doubt, and this was what he strove for most strenuously. Freedom of thought, like freedom of the Press, by no means implies that what is free must necessarily be good. In both cases there may be a rank growth of weeds, nurtured in vicious imagination, and finding a ready market with the credulous mob. For the detection and rejection of these, the critical method of science serves as well as it does against the loftier errors supported by authority. It was on Descartes and on Hume that Huxley founded the precise form in which he urged the duty of doubt, and his exact words are worth quoting. "It was in 1619, while meditating in solitary winter quarters, that Descartes (being about the same age as Hume when he wrote the _Treatise on Human Nature_) made that famous resolution, to "take nothing for truth without clear knowledge that it is such," the great practical effect of which is the sanctification of doubt; the recognition that the profession of belief in propositions, of the truth of which there is no sufficient evidence, is immoral; the discrowning of authority as such; the repudiation of the confusion, beloved of sophists of all sorts, between free assent and merely piously gagged dissent, and the admission of the obligation to reconsider even one's own axioms on due demand." This was the healthy and active scepticism which took no direct pleasure in doubting, but used doubt only as a means of making knowledge doubly secure, and which prevented false ideas being bolstered up by privilege or by tyranny. "The development of exact natural knowledge in all its vast range, from physics to history and criticism, is the consequence of the working out, in this province, of the resolution to take nothing for truth without clear knowledge that it is such; to consider all beliefs open to criticism; to regard the value of authority as neither greater nor less than as much as it can prove itself to be worth. The modern spirit is not the spirit 'which always denies,' delighting only in destruction; still less is it that which builds castles in the air rather than not construct; it is the spirit which works and will work 'without haste and without rest,' gathering harvest after harvest of truth into its barns and devouring error with unquenchable fire."