"An Analytical Inquiry into the Principles of Taste", 1805, was, however, Knight's most influential work in his lifetime. This book sought to explain the experience of 'taste' within the mind and to clarify the theorisation of the concept of the picturesque, following from the writings of William Gilpin and Uvedale Price on the subject. Knight's views on the aesthetics of the picturesque are also formed in engagement with Edmund Burke's emphasis on the importance of sensation, which Knight partly rejects in favour of a modified associationism. The philosophical basis of Knight's theories have implications for his account of the relationship between the 'beautiful' and the 'picturesque'. For Knight, aesthetic concepts cannot be formed directly from optical sensations, because these must be interpreted within the mind before they can be recognised as beautiful. Thus a Classical architecture Roman temple is beautiful because of the proportions of its parts, but these proportions can never be perceived directly by the senses, which will simply encounter a mass of confused impressions. 'Beauty' is thus a product of internal mental acts. It is therefore proper to speak of moral, mathematical and other non-sensuous forms of beauty, contrary to Burke, Hogarth and others who claimed such usages were metaphorical. In all cases 'the particular object proportion is an abstract idea.’