An enquiry concerning the principles of natural knowledge

by Alfred North Whitehead

[24.5] Amid the development of events the same non-delusive perceptual object may be perceived in a developed situation, again with 'legal' modifications of the association of perceived sense-objects. The verbal analysis of what constitutes a legal modification of the association without breach of the essence of the observed permanence would be impossibly complex in each particular case; but the judgment as to what is allowable in modification is immediate in practice, apart from exceptional cases.

A non-delusive perceptual object will be called a 'physical object.'

It is an essential characteristic of a physical object that its situation is an active condition for its perception. For this reason the object itself is often named as the cause. But the object is only derivatively the cause by its relation to its situation. Primarily a cause is always an event, namely, an active condition.

24.6 The apprehension of an event as the situation of a physical object is our most complete perception of the character of an event. It represents a fundamental perception of a primary law of nature. It is solely by means of physical objects that our knowledge of events as active conditions is obtained, whether as generating conditions or as transmitting conditions. For example, the mirror is recognised as a physical object and its situation is the generating condition for that association of sense-objects; but its situation is also a transmitting condition for the sense-objects and delusive perceptual objects which are perceived as images behind it. Again, the prism is a physical object and its situation is a transmitting condition for the sense-object which is the spectrum.

So far as it is directly perceived in its various situations, a physical object is a group of associations of sense-objects, each association being perceived or perceivable by a percipient object with an appropriate percipient event as its locus. But the object is more than the logical group; it is the recognisable permanent character of its various situations.

24.7 In spite of their insistence in perception these physical objects are infected with an incurable vagueness which had led speculative physics practically to cut them out of its scheme of fundamental entities. In the first place this vagueness arises from the unique situation of such an object within any small duration. The result is that the object is confounded with the event which is its situation. But a situation is prolonged in time, and a temporal part of that event is not the event itself. Now the object during ten seconds is not part of the object during one of these seconds. The object is always wholly itself during ten seconds or during one second. It is this train of thought which led to the introduction of the durationless instant of time as a fundamental fact, thus fatally confusing the philosophy of science. The error arose from not discriminating the object from its situation. The train of events which is the situation of the object through a prolonged stretch of time is not the unique object; it is the set of events with which the object has its unique association. The difficulty of this point of view arises from the fact that a temporal succession of events, each very similar to the others, ceases to mark for us the time-flux in comparison with the rhythmic changes of our bodies. The result is that in perceiving an unchanging cliff the recognition of permanence, i.e. of the object, overwhelms all other perception, the flux of events becoming a vague background owing to the absence of their demarcation in our perceptual experience.

24.8 The essential unity of the object amid the spatial parts of its situation is more difficult to grasp. The derivation of space and time by the method of extensive analysis, as explained in [Part III] of this enquiry, exhibits the essential identity of extension in time and extension in space. Thus the reasons for denying temporal parts of an object are also reasons for denying to it spatial parts. Again, it is true that the leg of a chair occupies part of the space which is occupied by the chair. But in appealing to space we are appealing to relations between events. What we are saying is, that the situation of the leg of the chair is part of the situation of the chair. This fact only makes the leg to be part of the chair in a mediate derivative sense, by way of their relations to their situations. But the leg is one object with a recognisable permanence of association, and the chair is another, with recognisable permanence of association distinct from that of the leg, and their situations in all circumstances have certain definite relations to each other expressible [5] in temporal and spatial terms.

24.9 The second reason for the vagueness of physical objects is the impossibility of submitting the group of associations, forming the object, to any process of determination with a progressive approximation to precision. A physical object is one of those entities of ordinary experience which refuse to be pressed into the service of science by way of a progressive exactness of determination. Consider for example a definite object such as a certain woollen sock. It wears thin, but it remains the same object; it is darned, and remains the same object; finally after successive repairs no part of the original wool is left, but it is the same sock. The truth is that each time we affirm the self-identity of this object we are construing the group of associations, which we recognise, in a more and more attenuated sense. The object which is both the sock at the end and the sock at the beginning is a very attenuated complex type of permanence, which would not be what we meant by the sock merely at the beginning of its career or as perceived merely at the end of its career. By insisting on the continued identity of the sock, we are in fact continually juggling with what we mean by the sock, always retaining the most complete associations which we can trace through the whole continuous series of events forming the successive situations of the sock. The physical object 'works' perfectly for the ordinary usage of life, and is thus fully justified for that purpose in the eyes of the pragmatic philosopher.

24.91 But these objects do represent essential facts of nature; sometimes, as it may seem to us, trivial facts not worth disentangling from the events which are their situations, sometimes useful facts. But their essential character is exemplified when we reach biological facts. A living organism exhibits a certain unity of being which is merely the exhibition of the enhanced importance of the unity of the physical object.

[25. Scientific Objects]. 25.1 The various types of scientific objects arise from the determination of the characters of the active conditioning events which are essential factors in the recognition of sense-objects.