"The history of science may be described as the breaking down, and the crumbling away, of artificially constructed barriers. All the great men of science have been famous wall-breakers. ...It is worthy to remark that the central conception of the alchemists ...was the unity of natural phenomena. ...[T]heir arguments would be somewhat as follows—Plants grow from seeds ...animals become larger, stronger, and more complete ...the plant may well be called more perfect than the seed, and the full grown animal more perfect than the immature ...both plants and animals grow, come to their prime, and decay; and there are degrees of perfection in the animal and vegetable worlds. Now—we may suppose the argument of the alchemist... minerals and metals and all inanimate things should grow, and change, from less perfect to more perfect forms; as there are degrees of perfectness and dignity in among all living things, so... among all things; some metals disappear in acrid liquids, and... are... easily worn away, they are readily melted and burnt to ; but some other metals are not swallowed up by corrosive liquids, nor... worn away with ease, nor readily changed in fire; there are evidently noble and base metals, perfect and imperfect metals; and as the less perfect seed... produces the more perfect plant... rendered yet more perfect by cultivation, so the imperfect metals change slowly into... more perfect, and this... can be hastened by man's art and devices. ...[L]iving things are more perfect that inanimate things ...[M]uch more must changes from immature to mature forms be constantly proceeding from dead things like minerals and metals ...[I]t is probable that the plasticity of the minerals and metals will be greater ...hence ...it will be a comparatively easy thing to grow a noble metal like gold from ignoble metals like and copper, although it is impossible to change one kind of animal into another or one sort of plant into another ... A vague conception of the unity of nature... led to little accurate knowledge..; all that could be done was to perform a vast number of inaccurate and incomplete experiments, and to state the results in loose and slipshod language of the vague but sonorous hypothesis which prompted the experiments. And so although the hypothesis postulated the unity of nature there was no unity in the experimental results... collected to support the hypothesis. ...A man who sets out to discover what is must endeavour to put aside all his notions of what ought to be; it is only when he has gained a solid foundation of verified and accurate facts that he may venture to make a definite guess concerning the cause ...but unless he makes clearly stated guesses ...scientific hypotheses—he will remain a mere collector of half facts ..."