One of the things I find so fascinating about psychedelics, LSD in particular:
Our brains do a good job of forming a model of the reality around us, but it's never perfect. While we're sober, our brains filter out a lot of the data that it deems irrelevant to our immediate survival, a process heavily informed by classical conditioning. Conditioning doesn't just apply to small habits, it applies to our very perception of reality: for example, the first time you visit a new place, such as a new job or a new school, it appears unfamiliar to you. As time goes on, the place becomes more and more familiar, as you learn to filter out more and more details. Therefore, the more familiar you become with something, the less accurate your perception of it becomes. Our biology permits far more accurate perception, but during homeostasis, most of it isn't available to our conscious attention. The truth is that reality is actually pretty alien and unfamiliar in its truest form, but we learn to filter that stuff out.
Enter LSD: a substance which disables much of the classical conditioning, temporarily. This isn't guaranteed to give us a more accurate model of reality, but it oftentimes does. I find the dilation of the pupil to be a perfect metaphor for this: LSD increases awareness to a point at which all those little details that we normally filter out manage to reach conscious awareness. Likewise, it expands the pupil such that it can absorb more light per unit of time, or per "frame". A common theme I hear reported from LSD users, and that I've experienced myself, is that spending time in a familiar environment (such as your home) makes you realize how unfamiliar the whole place feels. You look around and note that all of the objects are exactly where they were before, but somehow the place just feels different. The difference is that we are now perceiving it with more precision, and coming closer to the limits of what our biology permits (a level of accuracy which is actually quite astounding, as most users of LSD can attest to). The world feels anew, as if it were our first time observing it. We become like children, in a sense, with all the awe and wonder that accompanies experiencing the world as if it were our first time doing so, yet with an adult's ability to rationalize.
It's one of the most beautiful aspects of this compound, and I feel honored and privileged to have experienced it as many times as I have. I am proud to say that LSD has had a massively positive impact on my life, my relationships with other people, and my ability to love and appreciate this reality in which we find ourselves.