Humans have senses. We can sense light (via eyes), sound (via ears), pressure and temperature (via skin), chemical composition (via nose and tongue), balance and acceleration (via the vestibular labyrinthine system), and we can sense many other things via various organs in the body. All of these senses give use access to reality by creating sensations. As babies our impression of the world is “as one great blooming, buzzing confusion.” But as we mature and as our senses develop, our sensations about the world gain clarity.
The senses are physiological processes. As such they cannot be right or wrong. The senses simply do what they do regardless of how one might wish them to be. The senses receive input from the world. To use a metaphor, a television also receives input from a remote control. If we press the channel button, the picture on the screen will change. The concepts of right or wrong do not apply here. The process is purely causal.
Sensations lead to perception. Perception is an automatic process in mature adults. We cannot control it. When we dip a straight straw into our glass of water, we perceive the straw to be bent even though the straw is not bent in reality. This is not because our senses are wrong. This is due to the fact that water refracts light. If anything, this example show how good our eyes are at interpreting light traveling at different speeds through different mediums.
After we perceive something we make judgements. In the case of the straw in water we can use our reason to judge that straw really is not bent after all. Likewise through experience we can discern between optical illusions and reality. Unlike perception, judgements can be right or wrong. If we were to believe in magic after witnessing a performance by a magician, our judgement about what we perceived would be wrong.
Our access to reality starts with perceptions. As we gain experience, our judgements about what we perceive in reality will improve.