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 , as perceived in a situation which extends throughout a duration of a time-system , possesses a figure in , if every volume of , lying in a moment of inherent in , 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 the point of view of sense-figures are those which form present durations of perceptions—in general, those durations which are cogredient with a percipient event and are each short enough to form one immediate present. Thus in the numerous instances in which there is no large change within such an immediate present, there is a perceived figure. Accordingly we can define a sense-figure precisely as follows: The figure, for a time-system , of sense-object in situation is the relation holding, and only holding, between and any -volume congruent to a member of the set of -volumes of . This definition is only important when the -volumes of are all nearly congruent to each other; because only in that case is this relation recognisable in perception. 62.3 Thus, each sense-object is primarily capable of its own sort of sense-figure and of that sort only. There are the sense-figures of blue of one shade, and the sense-figures of blue of another shade, and the separate sets of figures belonging to all the shades of reds and greens and yellows. There is the set of figures of the touch of velvet, and the set of figures of the touch of marble at particular temperatures of hand and surface and with a particular polish of surface.