Complexity is in the eye of the beholder. To most people, a cat is simple and an atom is complex, but for a physicist the reverse is true. We need to be careful when defining complexity, so it isn't distorted by our biases. Human intuition expects simple behavior to have simple causes (i.e. a simple set of rules), and complex behavior to have complex causes, but this isn’t always the case. Do we perceive physical laws and processes (e.g. thermodynamics, molecular forces, interatomic forces, electrical firings in our own brain, the fact that objects appear to persist over time even though the subatomic particles comprising them blink into and out of existence, etc.) to be simple because they really are simple, or because our brains were shaped by evolution to perceive them in this way because it was survivally advantageous? In other words, it's obviously evolutionarily beneficial for us to perceive these things as simple, but can we step out of this bias and determine whether they really are objectively simple or not? Observed simplicities can't be totally incorrect misperceptions due to human ignorance, since they do have predictive validity (e.g. interpreting molecular velocities as temperature). But how close are our perceptions to the way things really are?