The dimmed outlines of phenomenal things all merge into one another unless we put on the focusing-glass of theory, and screw it up sometimes to one pitch of definition and sometimes to another, so as to see down into different depths through the great millstone of the world.
Interpretation
Understanding the world requires a theoretical framework to focus our observations.
James Clerk Maxwell expresses the idea that our perception of complex phenomena is often muddled and unclear. By applying theory as a lens, we can clarify and define our observations, allowing us to explore and understand the deeper layers of reality that might otherwise remain indistinct.
In practice
In a science class discussing the importance of theory in experimental design.
Science appears to us with a very different aspect after we have found out that it is not in lecture rooms only, and by means of the electric light projected on a screen, that we may witness physical phenomena, but that we may find illustrations of the highest doctrines of science in games and gymnastics, in travelling by land and by water, in storms of the air and of the sea, and wherever there is matter in motion.
... that, in a few years, all great physical constants will have been approximately estimated, and that the only occupation which will be left to men of science will be to carry these measurements to another place of decimals.
Very few of us can now place ourselves in the mental condition in which even such philosophers as the great Descartes were involved in the days before Newton had announced the true laws of the motion of bodies.
What's the go of that? What's the particular go of that?
I have also a paper afloat, with an electromagnetic theory of light, which, till I am convinced to the contrary, I hold to be great guns.
If we betake ourselves to the statistical method, we do so confessing that we are unable to follow the details of each individual case, and expecting that the effects of widespread causes, though very different in each individual, will produce an average result on the whole nation, from a study of which we may estimate the character and propensities of an imaginary being called the Mean Man.
Psychology has a long past, but only a short history.
I have come to the conclusion that Darwinism is not a testable scientific theory, but a metaphysical research programme.
Whoever, in the pursuit of science, seeks after immediate practical utility, may generally rest assured that he will seek in vain.
Mathematics is the key and door to the sciences.
Experimentation is the least arrogant method of gaining knowledge. The experimenter humbly asks a question of nature.
Certainly, it may bring to light such a deeper knowledge of the structure of matter as to constitute a veritable discontinuity in the progress of science.
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