Every entity has different properties and features such as color, shape, mass and texture. During the early days of the scientific revolution thinkers considered the fact that while some of these properties belong to the objects themselves, others are much more likely to be a product of our responses to these objects when we perceive them. Their properties such as size and shape are intrinsic to the objects, whereas properties such as warmth, texture, sound and color only exist as aspects of our existence.


Galileo illustrated this point by asking us to consider whether the tingle triggered by a tickly feather is a feature of the feather itself. If you were to stroke a marble statue with a feather, would a tickling sensation be produced? Of course not. The tingle is a sensation, felt on our skin, the feather merely possesses the capacity to provoke or cause the tingling sensation. The feather doesn't carry the tingle around on its tip, waiting for us to sense it.