History of the Intellectual Development of Europe, Volume II (of 2) / Revised Edition

by John William Draper

The apparent position of man on the heliocentric theory. [337] When the ancient doctrine of the plurality of worlds was restored by Bruno, Galileo, and other modern astronomers, the resistance it encountered was mainly owing to its anticipated bearing on the nature and relations of man. It was said, if round our sun, as a centre, there revolve so many planetary bodies, experiencing the changes of summer and winter, day and night—bodies illuminated by satellites, and perhaps enjoying twilight and other benefits such as have been conferred on the earth—shall we not consider them the abodes of accountable, perhaps of sinful, beings like ourselves? Nay, more; if each of the innumerable fixed stars is, as our sun, a central focus of light, [338] attended by dark and revolving globes, is it not necessary to admit that they also have their inhabitants? But among so many families of intelligent beings, how is it that we, the denizens of an insignificant speck, have alone been found worthy of God's regard?

It was this reasoning that sustained the geocentric theory, and made the earth the centre of the universe, the most noble of created things; the sun, the moon, the stars, being only ministers for the service of man.

The fallacy of objections to that theory.But, like many other objections urged in that memorable conflict, this was founded on a misconception, or, rather, on imperfect knowledge. There may be an infinity of worlds placed under the mechanical relations alluded to, but there may not be one among them that can be the abode of life. The physical conditions under which organization is possible are so numerous and so strictly limited that the chances are millions to one against their conjoint occurrence.

Evidence furnished by Geology.In a religious point of view, we are greatly indebted to Geology for the light it has cast on this objection. It has taught us that during inconceivable lapses of time our earth itself contained no living thing. These were those preorganic ages to which reference was made in the last chapter. Then by slow degrees, as a possibility for existence occurred, there gradually emerged one type after another. It is but as yesterday that the life of man could be maintained.

The transitory nature of living forms.Only in the presence of special physical conditions can an animal exist. Even then it is essentially ephemeral. The life of it, as a whole, depends on the death of its integrant parts. In a waterfall, which maintains its place and appearance unchanged for many years, the constituent portions that have been precipitated headlong glide finally and for ever away. For the transitory matter to exhibit a permanent form, it is necessary that there should be a perpetual supply and also a perpetual removal. So long as the jutting ledge over which the waters rush, and the broken gulf below that receives them, remain unchanged, the cataract presents the same appearance. But variations in them mould it into a new shape; its colour changes with a clear or [339] cloudy sky; the rainbow seen in its spray disappears when the beams of the sun are withdrawn.

So in that collection of substance which constitutes an animal; whatever may be its position, high or low, in the realm of life, there is a perpetual introduction of new material and a perpetual departure of the old. It is a form, rather than an individual, that we see. Its permanence altogether depends on the permanence of the external conditions. If they change, it also changes, and a new form is the result.

Characteristics of animal life.An animal is therefore a form through which material substance is visibly passing and suffering transmutation into new products. In that act of transmutation force is disengaged. That which we call its life is the display of the manner in which the force thus disengaged is expended.

Matter and force.A scientific examination of animal life must include two primary facts. It must consider whence and in what manner the stream of material substance has been derived, in what manner and whither it passes away. And, since force can not be created from nothing, and is in its very nature indestructible, it must determine from what source that which is displayed by animals has been obtained, in what manner it is employed, and what disposal is made of it eventually.

Force is derived from the sun.The force thus expended is originally derived from the sun. Plants are the intermedium for its conveyance. The inorganic material of a saline nature entering into their constitution is obtained from the soil in which they grow, as is also, for the most part, the water they require; but their organic substance is derived from the surrounding atmosphere, and hence it is strictly true that they are condensations from the air.

Mode in which plants obtain material substance.These statements may be sufficiently illustrated, and the relation between plants and animals shown, by tracing the course of any one of the ingredients entering into the vegetable composition, and derived, as has been said, from the air. For this purpose, if we select their chief solid element, carbon, the remarks applicable to the course it follows will hold good for other accompanying elements. It is scarcely [340] necessary to embarrass the brief exposition of vegetable life now to be given by any historical details, since these will come with more propriety subsequently. It is sufficient to mention that the chemical explanations of vegetable physiology rest essentially on the discovery of oxygen gas by Priestley, of the constitution of carbonic acid by Lavoisier, and of water by Cavendish and Watt.