Speculative Philosophy is the endeavour to frame a coherent, logical, necessary system of general ideas in terms of which every element of our experience can be interpreted. By this notion of ‘interpretation’ I mean that everything of which we are conscious, as enjoyed, perceived, willed, or thought, shall have the character of a particular instance of the general scheme. Thus the philosophical scheme should be coherent, logical, and, in respect to its interpretation, applicable and adequate. Here ‘applicable’ means that some items of experience are thus interpretable, and ‘ade- quate’ means that there are no items incapable of such interpretation.
‘Coherence,’ as here employed, means that the fundamental ideas, in terms of which the scheme is developed, presuppose each other so that in isolation they are meaningless. This requirement does not mean that they are definable in terms of each other; it means that what is indefinable in One such notion cannot be abstracted from its relevance to the other notions. It is the ideal of speculative philosophy that its fundamental no- tions shall not seem capable of abstraction from each other. In other words,’ it is presupposed that no entity can be conceived in complete abstraction from the system of the universe, and that it is the business of speculative philosophy to exhibit this truth. This character is its coherence.
The term ‘logical’ has its ordinary meaning,’ including ‘logical’ con- sistency, or lack of contradiction, the definition of constructs in logical terms, the exemplification of general logical notions in specific instances, and the principles of inference. It will be observed that logical notions must themselves find their places in the scheme of philosophic notions.
It will also be noticed that this ideal of speculative philosophy has its rational side and its empirical side. The rational side is expressed by the terms ‘coherent’ and ‘logical.’ The empirical side is expressed by the terms ‘applicable’ and ‘adequate.’ But the two sides are bound together by clearing away an ambiguity which remains in the previous explanation of the term ‘adequate.’ The adequacy of the scheme over every item does not mean adequacy over such items as happen to have been considered. It means that the texture of observed experience, as illustrating the philo- sophic scheme, is such that all related experience must exhibit the same texture. Thus the philosophic scheme should be necessary,’ in the sense of bearing in itself its own warrant of universality throughout an experience, provided that we confine ourselves to that which communicates with im- mediate matter of fact. But what does not so communicate is unknow-able, and the unknowable is unknown; and so this universality defined by ‘communication’ can suffice.
This doctrine of necessity in universality means that there is an essence to the universe which forbids relationships beyond itself, as a violation of its rationality. Speculative philosophy seeks that essence.
(Alfred North Whitehead, “Process and Reality: An Essay in Cosmology”)