The first of the three points we have called attention to has, so to

speak, become famous through the lectures of du Bois-Reymond, which

attracted much attention, on "The Limits of Natural Knowledge," and "The

Seven Riddles of the Universe." That these thoughtful lectures made so

great an impression did not mean that a great new discovery had been made,

but was rather a sign of the general lack of reflection on the part of the

public, for they only expressed what had always been self-evident, and

what had only been forgotten through thoughtlessness, or concealed by

polemical rhetoric. Consciousness, thought, even the commonest sensation

of pleasure and pain, or the simplest sense-perception, cannot be compared

with "matter and energy," with the movements of masses. They represent a

foreign and altogether inexplicable guest in this world of matter,

molecules, and elements. Even if we could follow the play of the nervous

processes with which sensation, consciousness, pain, or pleasure are bound

up, into their most intricate and delicate details, if we could make the

brain transparent, and enlarge its cells to the size of houses, so that,

with searching glance, we could count and observe all the processes, and

even follow the dance of the molecules within it, we should never see

"pain," "pleasure," or "thought," or anything more than bodies and their

movements. A thought, such as, for instance, the perception that two and

two make four, is not long or broad, above or beneath; it cannot be

measured or weighed in inches or pounds like matter, tested with the

manometer, thermometer, or electrometer for its potential or intensity and

tension, measured by amperes or volts or horse-powers like energies and

electric currents; it is something wholly different, which can be known

only through inner experience, but which is much better known than

anything else whatever, and which it is absolutely impossible to compare

with anything but itself. Even if we admit that it can only become actual

and develop as an accompaniment of processes within bodies, and only

within those bodies we call "living," and that wherever bodies exist

psychical phenomena occur; even if we were able, as we never shall be

able, to produce living beings artificially in a retort, and even if

psychical phenomena occurred in these also, we should still have made no

progress towards explaining what the psychical really is. It would still

only be the blazing up in these bodies of a flame which, in some

inexplicable way, had fallen upon them, and associated itself with them.

We do not doubt that this association, where it takes place, does so in

obedience to the strictest law and the most inexorable necessity;

therefore, that wherever and however the corporeal conditions are

produced, sensation and consciousness will awaken. For we believe in a

world governed by law. But the mystery is in no way lessened by this, and

the modern theory of evolution throws no light into this utterly

impenetrable darkness. In the first place, the whole idea of "explaining"

in terms of "evolution" is a futile one. The process of becoming is

pictured as a simple process of cumulation, a gradual increase of

intensities, while the business is really one of change in quality and the

introduction of what is new. In the second place, the occurrence even of

the first and most primitive sensation contains the whole riddle

concentrated on a single point. In the third place, the riddle meets us

anew and undiminished in every developing individual. For to say that the

physical inwardness, once it has arisen, is "transmitted," is not an

explanation but merely an admission that the riddle exists. And the idea

that the psychical is just a penumbra or shadow of reality, which comes of

itself and so to speak gratis, is quite inadmissible from the point of

view of strict natural science. There are no longer luxus and lusus

naturae. Reality cannot throw a "shadow." According to the principles of

the conservation of matter and energy, we must be able to show whence it

gets the so-called shadow, and with what it compensates for it.