here or other it comes across something in the world which it
cannot bring under that principle. Then it is left with two equally
ultimate existences, neither of which can be derived from the other.
Thus it breaks out into dualism.

Now the search for a monistic explanation of things is a universal
tendency of human thought. Wherever we look in the world of thought,
we find that this monistic tendency appears. I have already said that
it appears throughout the history of philosophy. It reveals itself,
{64} too, very clearly in the history of religion. Religion begins in
polytheism, the belief in many gods. From that it passes on to
monotheism, the belief in one God, who is the sole author and creator
of the universe. In Hindu thought we find the same thing. Hindu
thought is based upon the principle that "All is one." Everything in
the world is derived from one ultimate being, Brahman. But not only is
this monistic tendency traceable in religion and philosophy; it is
also traceable in science. The progress of scientific explanation is
essentially a progress towards monism. In the first place, the
explanation of isolated facts consists always in assigning causes for
them. Suppose there is a strange noise in your room at night. You say
it is explained when you find that it is due to the falling of a book
or the scuttling of a rat across the floor. The noise is thus
explained by assigning a cause for it. But this simply means that you
have robbed it of its isolated and exceptional position, and reduced
it to the position of an example of a general law. When the water
freezes in your jug, you say that the cause of this is the cold. It is
an example of the law that whenever the cold reaches a certain degree,
then, other things being equal, water solidifies. But to assign causes
in this way is not really to explain anything. It does not give any
reason for an event happening. You cannot see any reason why water
should solidify in the cold. It merely tells us that the event is not
exceptional, but is an example of what always happens. It reduces the
isolated event to a case of a general law, which "explains," not
merely this one event, but possibly millions of events. It is not
merely that cold solidifies the water in your jug. {65} It equally
solidifies the water in everybody's jug. The same law "explains" all
these, and likewise "explains" icebergs and the polar caps on the
earth and the planet Mars. In fact scientific explan