Our awareness of the material world requires physical receptors, the five senses which enable us to see, hear, feel, taste and smell. These reveal our environment to us, but only those selected aspects of it in relation to which we have to act and react. For in selecting, our senses exclude much more than they let in. They have developed to aid our survival as organisms occupying our particular evolutionary niche, and they accordingly function as meshes through which only a certain range of signals can pass.

If the whole range of light waves affected us, we would be unable to distinguish objects affecting our survival. If every sound wave registered in our consciousness, we would be so confused by the universal cacophony as to be unable to react to the sounds that we need to hear.

The process by which we are aware of the physical environment is extremely complex. It is also normally a successful process as otherwise the species would not have survived. Each species has been programmed through the evolutionary process to interpret the signals of the physical environment correctly as they affect that particular life form, and this applies to humans too. There are of course some cultural differences, although these do not affect the basic fact that we have very little cognitive freedom at this level of awareness.