​Chapter 1

You want to account for the existence of another world — a register of reality alongside the physical one, populated by beings that act on ours. Gods, spirits; the label matters less than the question: how would such a thing be possible?

To exist is to affect something. A affects B, and that is enough for A to exist for B; whether B affects A in return is a separate question. Physics says yes, but the definition carries no such requirement. Symmetry of interaction is a regularity drawn from observation, and thought can suspend it.

Lift symmetry, and several possibilities appear. A and B may affect each other in the same way, but the effects are incommensurable — A reshapes B, B barely scratches A. Or A affects B and B has no way of affecting A at all. Or A affects B through one medium and B affects A through an entirely different one. Or A affects B and B, instead of affecting A back, affects C, the impact propagates elsewhere. Each of these satisfies the existence criterion for A and violates symmetry alone.

The strongest case, when A affects B and B has no way of affecting A, is Sagan's dragon in the garage: a dragon that cannot be seen, heard, or touched, that leaves no trace. Sagan's point was that such a being is indistinguishable from no being at all. But indistinguishable for whom? For A's instruments, which are calibrated to detect effects within A's own world. If B acts on A at a level A cannot measure then the dragon is still real. The question becomes: where is the threshold?

Physics offers an analogue. Quantum mechanics assigns a state to a system as a superposition of possible outcomes. Older presentations spoke of collapse: measurement selects one result and erases the rest; current treatments center on decoherence. When a quantum system couples to a macroscopic environment, phase relations between alternatives disperse with extreme speed, and it begins to behave as if it were in a classical mixture rather than a coherent superposition. Decoherence explains why the world presents stable classical states to observation, but it does not know why one outcome is realized rather than another.

Now suppose an agent from another world acts in that gap. It does not break conservation laws: its action enters where decoherence has already destroyed the phase that sustained the superposition, where physics still passes from admissible outcomes to one actual branch. The intervention is minimal: a bias at the threshold where alternatives have become classically separated but actuality has not yet been assigned. Inside world A, instruments register only noise or luck.

A glass standing on a table could, under quantum mechanics alone, appear on the other side of the room: all particles tunneling simultaneously in the same direction. The probability lies so close to zero that the age of the universe gives no practical hope of seeing it, but the laws permit it.

Thus, asymmetric interaction between worlds is coherent. The acausal agent from world B acts in the blind zone left between decoherence and realized outcome. Observed reality already contains asymmetry. A small perturbation in initial conditions can ramify into vastly different outcomes. Prions reshape proteins without being reshaped in return, propagating misfolding through contact alone. Or a signal can influence a receiver without the receiver altering the source, as in a one-way broadcast.

We built four modes of asymmetric interaction, drew their consequences, and none of this was given in experience. No one has observed a being from another world tilting a wavefunction. The four modes are products of pure thought — and that demands an account.

The most basic act the mind performs is differentiation. Sensation is differentiation: red and blue, hard and soft — each differentiates one quality from another, delivered through qualia, the raw feel of the difference. An animal lives at this level. A predator charges; the prey differentiates speed and shape, and runs.

Differentiation rises in layers. From sensory differentiation comes pattern recognition: the prey not only flees but anticipates based on repeated encounters. Apply differentiation to these patterns, and abstraction begins: shapes become symbols, sounds become signals. Language arises here, as differentiation hardens into naming. A repeated sound associated with a threat becomes a word "danger", detached from the sensation. The word can now be manipulated in the absence of the referent: "Danger may come tomorrow." Apply differentiation again, and a further level emerges. Regularities of language, laws that govern classes of patterns. Each turn produces a higher level, farther from sensation, freer. The second level handles things through concepts in their absence, the third uses concepts as objects. There is no ceiling; each level is material for the next.

The second level of differentiation is discursive thought, discursion. The thought experiment that opened this chapter used it: we took a regularity, handled it as an object, removed a constraint, and examined the result. The ideal, the domain where discursion lives, is free to work with any pattern, including patterns never encountered in experience.

Plato named it the world of forms, the eide, perfect originals of which the physical world is a shadow. The discovery was genuine, but Plato turned the ideal into law. The forms became eternal, unchanging, governing, with the Good at the top, everything else subordinate. The world of ideas became second nature, a higher (meta-) physics.