The contradictory opposite, _i.e._, the denial of necessity, is _contingency_. The content of this conception is, therefore, negative—nothing more than this: absence of the connection expressed by the principle of sufficient reason. Consequently the contingent is also always merely relative. It is contingent in relation to something which is not its reason. Every object, of whatever kind it may be—for example, every event in the actual world—is always at once necessary and contingent, _necessary_ in relation to the _one_ condition which is its cause: _contingent_ in relation to everything else. For its contact in time and space with everything else is a mere coincidence without necessary connection: hence also the words chance, συμπτωμα, _contingens_. Therefore an absolute contingency is just as inconceivable as an absolute necessity. For the former would be simply an object which stood to no other in the relation of consequent to its reason. But the inconceivability of such a thing is just the content of the principle of sufficient reason negatively expressed, and therefore this principle must first be upset before we can think an absolute contingency; and even then it itself would have lost all significance, for the conception of contingency has meaning only in relation to that principle, and signifies that two objects do not stand to each other in the relation of reason and consequent.
In nature, which consists of ideas of perception, everything that happens is necessary; for it proceeds from its cause. If, however, we consider this individual with reference to everything else which is not its cause, we know it as contingent; but this is already an abstract reflection. Now, further, let us abstract entirely from a natural object its causal relation to everything else, thus its necessity and its contingency; then this kind of knowledge comprehends the conception of the _actual_, in which one only considers the _effect_, without looking for the cause, in relation to which one would otherwise have to call it _necessary_, and in relation to everything else _contingent_. All this rests ultimately upon the fact that the _modality_ of the judgment does not indicate so much the objective nature of things as the relation of our knowledge to them. Since, however, in nature everything proceeds from a cause, everything _actual_ is also _necessary_, yet only so far as it is _at this time, in this place;_ for only so far does determination by the law of causality extend. Let us leave, however, concrete nature and pass over to abstract thinking; then we can present to ourselves in reflection all the natural laws which are known to us partly _a priori_, partly only _a posteriori_, and this abstract idea contains all that is in nature at _any_ time, in _any_ place, but with abstraction from every definite time and place; and just in this way, through such reflection, we have entered the wide kingdom of _the possible_. But what finds no place even here is the _impossible_. It is clear that possibility and impossibility exist only for reflection, for abstract knowledge of the reason, not for knowledge of perception; although it is the pure forms of perception which supply the reason with the determination of the possible and impossible. According as the laws of nature, from which we start in the thought of the possible and impossible, are known _a priori_ or _a posteriori_, is the possibility or impossibility metaphysical or physical.