Having laid the ground for their rejection of established theories of the origin of social institutions the Scots are then free to develop their own understanding of how such institutions came about. As intimated in the previous chapters, this understanding is strongly grounded in notions of habit. The Scots regard habit as a universal attribute of human nature. Ferguson defines a habit as ‘the acquired relation of a person to the state in which he has repeatedly been’ (Ferguson 1973 vol. 1: 209), while Hume argues, with relation to the habitual behaviour of all animals, that what is commonly referred to as instinct, can in fact be understood as a form of habitual behaviour. Indeed he regards habit as ‘one of the principles of nature’ (THN: 179).