"I believe it is more akin to psychology," the voice interrupted.
"How so?" He still looked at the wall.
"Because it concerns the control of other beings, the summoning of them, and the constraining of them to perform certain actions."
"Good. That is very suggestive. Fortunately, formulas may still hold good so long as their reference is clear, though we are ignorant of the precise nature of the entities to which they refer. For example, a physicist need not be able to give a visual description of an atom, even if the term visual appearance has any meaning when applied to an atom—which is doubtful. Similarly, a sorcerer need not be able to describe the appearance and nature of the entity he summons. But the point is well taken. Many seemingly impersonal forces, when broken down sufficiently, become something very much like personality. It's not too far-fetched to say that it would take a science resembling psychology to describe the behavior of a single electron, with all its whims and impulses, though electrons in the aggregate obey relatively simple laws, just as human beings do when considered as crowds. The same holds true of the basic entities of magic, and to a much greater degree.
"It is partly for this reason that magical processes are so tricky and dangerous, and why their working can be so readily impeded if the intended victim is on guard against them—as your formulas have to our knowledge been nullified since Mrs. Gunnison stole your book. That one formula I used on Sunday night worked only because it was not anticipated that I would be the operator. And even at that its working was greatly hindered."
His words possessed for him an incredibly strange overtone. But it was only by maintaining a dry, scholarly manner that he could keep going. He knew that at the first touch of casualness or informality, the latent morbidity of the situation would engulf him.
"There remains one all-important consideration," he went on swiftly. "Magic appears to be a science which markedly depends on its environment—that is, the situation of the world and the general conditions of the cosmos at any particular time. For example, Euclidean geometry is useful on Earth, but there are regions—and it would be easy to imagine more—in which a non-Euclidean geometry is more practical. The same is true of magic, but to a more striking degree. The basic, unstated formulas of magic appear to change with the passage of time, requiring frequent restatement—though it might conceivably be possible to discover master-formulas governing that change. It has been speculated that the laws of physics show a similar evolutionary tendency—though if they do evolve, it is at a much less rapid rate than those of magic. It is natural that the laws of magic should evolve or change more swiftly, since magic depends on a contact between the material world and another level of being—and that contact is complex and may be shifting rapidly.
"Take astrology, for example. In the course of several thousand years, the precession of the equinoxes has put the Sun into entirely different celestial houses—signs of the Zodiac—at the same times of year. A person born, say, on March 22nd, is still said to be born in Aries, though he is actually born when the Sun is in the constellation Pisces. A failure to take into consideration this evolutionary change since the formulas of astrology were first discovered, has rendered the formulas obsolete and invalidated them for—"
"It is my belief," the voice broke in, like a phonograph suddenly starting, "that astrology has always been largely invalid. That it is one of the many pretended sciences which have been confused with true magic and used as a kind of window dressing. Such is my belief."