Sensory organs are the only channels of communication between the brain and the outside world. Simply put, the brain is not designed to sense on its own. For instance, an exposed brain would neither sense light shining on it nor feel something touching it. In fact, patients are often kept awake during brain surgery, which can help a surgeon isolate specific regions of the brain. The ancient Greek philosopher Aristotle recognized this characteristic of the brain over 2,000 years ago when he said, "Nothing is in the mind that does not pass through the senses." This concept can be seen clearly when volunteers are blind‐folded and placed in the warm water of a sensory deprivation tank. They soon experience visual, auditory, and tactile (touch) hallucinations, as well as incoherent thought patterns. From these experiments and others, it is apparent that we need constant input from our senses to carry out functions that give us personality and intellect.