The wheel is an extension of the foot, the book is an extension of the eye, clothing an extension of the skin, electric circuitry an extension of the central nervous system.
Marshall McLuhanFor those for whom the sex act has come to seem mechanical and merely the meeting and manipulation of body parts, there often remains a hunger which can be called metaphysical but which is not recognized as such, and which seeks satisfaction in physical danger, or sometimes in torture, suicide, or murder.
Marshall McLuhan