Again, the undulatory theory of Light. Studying the phenomena of a vast number of coloured and bright bodies, Science finds that it can think about these phenomena--can generalise and tie them into bundles best by _assuming_ that the bodies are all in a state of vibration; a vibration so minute that (unlike the vibrations connected with Sound) it cannot be directly perceived. So far good. There is no harm in the assumption of vibration, as long as it is understood to be a mere assumption for a temporary convenience of thought. But now Science goes farther than this, and not only supposes a common attribute to all visible bodies, but credits this common attribute with a real existence independent of the visible bodies in which it was supposed to inhere--and makes this the _cause_ of their visibility! Obviously now a common and universal medium is required for this common and universal assumed vibration (just as Newton required a medium for his universal "falling")--and so, hey presto! we have the Undulatory Ether. And having got it we find that to fulfil our requirements it must have a pressure of 17 million million pounds on the square inch, and yet be so rare and tenuous as not to hinder the lightest breath of air; that while it is thus rare enough to surpass all our powers of direct scrutiny, its vibrations must yet be capable of agitating and breaking up the solidest bodies; that it must pass freely through some dense and close structures like glass, and yet be excluded by some light and porous, like cork, and so on and on! In fact we find that it is unthinkable. Against this adamantine, impalpable Ether, as against this instantaneous, untranslatable gravitation, Science bangs its devoted head in vain. Having created these absurdities by the method of "personification of abstractions"[25] or the "reification of concepts,"[26] it seriously and in all good faith tries to understand them; having dressed up its own Mumbo Jumbo (which it once jeered at religion for doing) it piously shuts its eyes and endeavours to believe in it.