What is rewarding about understanding?
The traditional answer is that truth is intrinsically valuable. The Spinozist answer is that adequate ideas increase our power of acting. The more basic the answer the better, so perhaps a more mechanistic one?
Understanding is rewarding because it reduces cognitive entropy.
Before understanding, the organism has fragmented, competing, or contradictory models. There are loose ends, unresolved questions, uncertainty, and prediction errors. The nervous system is carrying many partially organized representations. Then comes understanding and the "aha." Nothing external may have changed, but internally a more coherent model of reality has emerged. Ten disconnected pieces suddenly fit into one explanatory structure. That is an anti-entropic event. The nervous system has literally become more organized.
This also explains why genuine understanding feels so different from merely receiving information what Spinoza emphasizes many times. Reading ten random facts often produces no satisfaction at all. Understanding one principle that unifies those ten facts can produce intense pleasure. The pleasure comes not from accumulating data but from compressing complexity into order. Information increases. Entropy decreases. Coherence increases.
This also suggests a beautiful reinterpretation of adequate ideas. An adequate idea is not simply one that corresponds better to reality. It is one that organizes many previous fragments into a coherent whole while improving the organism's capacity to predict and act which is already changing reality. That corresponds to what modern neuroscience often describes as efficient internal models.
There is another implication. Why do conspiracy theories feel so attractive? Because they also reduce cognitive entropy. They take a chaotic world and produce a single explanatory story. The problem is not that they fail to reduce entropy. The problem is that they often reduce it by sacrificing correspondence with reality. So there are two dimensions. One is internal coherence. The other is external adequacy. A healthy mind needs both. This is where Spinoza still has something important to contribute. He insists that understanding is not merely subjective coherence. It must correspond to the causal order of Nature.
Finally, the anti-entropic framework also explains why philosophy has survived for over two thousand years. People often think philosophy exists because humans enjoy abstract speculation. Again, a basic and deeper reason is that philosophy occasionally produces large-scale reductions in cognitive entropy. A philosophical insight does not merely answer one question. It reorganizes hundreds of previous experiences. Suddenly memories, emotions, observations, and concepts that had been isolated become parts of one intelligible structure. The organism experiences that as relief. This is the "aha" moment (but again not awakening). Not because philosophy is mystical. But because fragmentation has been replaced by organization.
The anti-entropy proposition has considerable explanatory power. It links Spinoza's adequate ideas, predictive processing, learning, and the cute Piranesi's ordinary tasks. Washing clothes reduces entropy in the environment. Understanding a difficult philosophical idea reduces entropy in the cognitive architecture. They occur at different scales, but they share the same functional pattern: they transform a more disordered state into a more ordered one.
But an addition is needed here that order alone is not enough. A perfectly organized delusion also reduces subjective fragmentation. What distinguishes scientific understanding, and what Spinoza hoped adequate ideas would achieve, is that the increase in internal order is constrained by the causal structure of the world. That is why the orbiting fits so well. The goal is not simply to maximize coherence, but to let coherence be continuously corrected by reality.