Page:An Enquiry Concerning the Principles of Natural Knowledge.djvu/204



62. Sense-Figures. 62.1 There are two types of objects which can be included under the general name of ‘figures’; objects of one type will be termed ‘sense-figures,’ and of the other type ‘geometrical figures.’

Figures of either type arise from the perception of the relation of sense-objects to the properties which their situations have in respect to their relations of extension with other events. The primary type of figure is the sense-figure and the geometrical figure is derivative from it.

62.2 Every sort of sense-object will have its own peculiar sort of sense-figure. The sense-figures associated with some sorts of sense-objects (e.g. smells and tastes) are barely perceptible, whereas the sense-figures associated with other sorts of sense-objects (e.g. sights and touches) are of insistent obviousness. The condition that a sense-object should have a figure within a given duration can be precisely stated: A sense-object O, as perceived in a situation σ which extends throughout a duration d of a time-system α, possesses a figure in d, if every volume of σ, lying in a moment of α inherent in d, is congruent with every other such volume.

Owing to the inexactitude of perception small quantitative defects from the rigorous fulfilment of this condition do not in practice hinder the perception of figure. Namely, the possession of sense-figure follows from the sufficiently approximate fulfilment of this condition. The durations which are important from