Atomic physics has achieved the status of common sense. It is hard now to understand why it took so long to arrive at it. Despite the efforts of a couple of pre-Socratics, it took till the nineteenth and twentieth century till atomic physics came into its own, driven by technology. People just didn’t have the idea of the minute constituents of matter, largely uniform, and constituting the whole of the physical universe. They didn’t envisage a hidden particulate (“corpuscular”) level of physical reality. Same with biology: biologists didn’t get the idea of the cell till fairly late in the game, let alone the molecular structure of the gene. Now biology is an atomic biology: bodies made of organs, organs made of sub-organs, sub-organs made of cells, cells made of nuclei, mitochondria, and other tiny structures, and so on down to biochemical molecules. Atomic physics and atomic biology are just part of the modern intellectual landscape, despite being invisible for centuries. But there is no such thing as atomic psychology. You would think that atomic psychology should be well developed by now, given our close proximity to the mind; but in fact, it doesn’t exist even as a twinkle in the eye of the aspiring mind scientist (I use that phrase because the term “psychologist” conjures up a rather limited picture of what a student of the mind might hope to produce). Why aren’t the atoms of mind staring us in the face, if there are such? Is it because the atomic conception simply doesn’t fit the mind? However, there are reasons to believe that some sort of atomic psychology must be true, even if it is not evident to us introspectively. First, it is hard to believe that mental states, as they are phenomenologically presented and commonsensically conceived, are ontologically primitive; it is hard to believe they have no further analysis—decomposition, part-whole hierarchy. What, do they just spring into being as they are as indivisible wholes? Is there no micro to their macro? Clearly, some kind of breakdown does exist, because there are complex mental states that are composed of simpler mental states (e.g., regret is composed of belief and desire). Also, propositional attitudes have complex conceptual content—propositions are decomposable entities. So, why shouldn’t the breakdown go deeper? Second, there appear to be commonalities between mental states that suggest recurring constituents: for example, pains, though very various, all partake of a single phenomenological quality—painfulness. Indeed, aversive mental states generally share a phenomenological feature: fear, hunger, and sexual frustration all display a quality of disagreeableness that marks them as belonging together. So, is there a psychological atom corresponding to this trait—the “nasty-tron”? It is negatively charged, like the electron, and unlike the “fun-tron” that corresponds to pleasant feelings, which is positively charged (I speak metaphorically). Why not suppose that there is a deeper level of psychological atoms underlying anything we can detect introspectively? Why not go the whole hog and see where this idea takes us—to a panoply of finitely many psychic particles that exist in the mind-brain and combine together to yield what we know as the mind? These particles could constitute a kind of periodic table of psychic elements—the basic constituents of the psychological universe. The situation is analogous to what obtains in linguistics (which is close to psychology): from sentences to phrases to words to morphemes to underlying constituents of morphemes.In other words, the brain is a place where the atoms of mind and language live, hitherto evading inspection. The brain is made of biological cells (neurons—note the suffix), which are made of molecules and atoms, and it is also made of psychical cells that break down further into more elementary components. Then, we achieve unification with physics and biology: psychology emerges as also atomic in structure. There is macro psychology and micro psychology, big mind and little mind. As a bonus, we might find that micro psychology brings us closer to understanding the mind-brain link, because the psychic particles are more intimately tied to the physics of the brain (they might not look much like the macro mental states they constitute). Possibly these mental particles are to be found outside the brain too, so that we end up embracing a sort of panpsychism (God help us), but they might also be peculiar to the brain for some reason. In either case, the mind comes to have an atomic architecture: the gross resulting from the miniscule, the observable composed of the unobservable. It has its lines and points, its planes and solids. The mind scientist will want to trace these compositional relations, discover their laws, and formulate theories that impose order on multiplicity. When asked what his academic specialty is he will say, “Atomic psychology”. Others in his department might reply, “Macro psychology” or “Cosmo-psychology” (aka “social psychology”). Maybe there will be a small sub-department devoted to interdisciplinary work between physicists and atomic psychologists called “Department of Micro Cognitive and Physical Science” (mainly consisting of string theorists and people called “bling theorists”—the ultimate particles of the mind being deemed “incandescent” in some way). The excitement will be palpable, yet dignified—after all, this is Deep Stuff. Seriously, though, we should not dismiss the idea of atomic psychology; and isn’t this what many psychologists have hankered after these many years—simple unanalyzable sensations, elementary conditioned reflexes, “bits” of information, units of psychic force, just noticeable differences, unconscious primitive drives, discrete bumps on the skull, IQ points, little homunculi in the head? Maybe one day atomic psychology will reach maturity just like atomic physics and atomic biology.
 Much the same is true of what might be called “atomic logic”—analyzing propositions and their logical relations in terms of logical atoms and their molecular compounds; indeed, just this terminology already exists.
 We could also say that mental states must already be partly composed of physical atoms, since their causal powers rely on the actions of physical atoms ultimately. If causal role is intrinsic to mental states, and causal role requires physical implementation, then mental states must harbor a physical atomic structure somewhere in their total constitution. This would mean that pains, for example, have both a physical and a mental atomic nature—both sorts of atoms exist within them. They are not as simple as they seem. The brain is a kind of atomic hothouse, contrary to initial appearances. It is not an undifferentiated grey lump or a continuous flowing river.