What does perception depend upon?

What does perception depend upon? Perception depends upon the memory of past perceptions. We identify our perceptions, through our identification of our past, similar perceptions. Should perception be completely free, from past perceptions? Human beings, tend to disagree. We have to depend on our past perceptions, because it makes identifying our present and future perceptions easier. Or, that is our perception. But is the immediate earlier perception, a valid perception? Why do human beings make so many faulty perceptions, if such be the case? And, then, why do they mind doing so? Perception is instantaneous, so why do we deliberate on our perceptions?