DETERMINACIONES EN EL CULTIVO

That which in its connection with the actual is determined in accordance with universal conditions of experience, is (that is, exists as) necessary.

The third postulate is concerned not with logical or formal necessity, but with “material necessity in existence”. This is in line with the emerging trend to distinguish between logical modality, i.e. a matter of lack of con- tradiction amongst concepts, and the kind of modality that involves, in addition, a relation to (i.e. determination by) the universal conditions of experience.

Lastly, as regards the third postulate, it concerns material ne- cessity in existence, and not merely formal and logical necessity in the connection of concepts. Since the existence of any object of the senses cannot be cognized completely a priori, but only comparatively a priori, relatively to some other previously given existence; and since, even so, we can then arrive only at such an existence as must somewhere be contained in the context of the experience, of which the given perception is a part, the neces- sity of existence can never be cognized from concepts, but always only from connection with that which is perceived, in accordance with universal laws of experience. (A226-7/B279)

There is an important clarification to be made here. One might think, given the account of possibility, that necessity of an object would be a mere matter of following from the laws of experience. But this turns out to be relative to some other previously given experience. So rather than an object being necessary when its existence (or something’s falling under the concept of the object) follows from the universal conditions of experience, it is nec- essary when it follows from a given experience plus the universal conditions of experience. Note again that this conditional necessity is restricted to the domain of objects of experience. Again, this guards against being able to argue for the necessary existence of a transcendent God, but may also cause problems for an account of mathematical and abstract objects.

An initial problem is how to distinguish these conditional necessities from those indirectly-experienced actualities inferred from directly-experienced actualities and the laws of experience, e.g. magnetic force as inferred from the behaviour of iron filings. Doesn’t this make either magnetic force (qua indirectly-perceived actuality) conditionally necessary, or conditional neces- sities merely actual? In response, one might say that certain events or entities can be conditionally necessary, whilst being ultimately or uncondi- tionally merely actual. E.g., one might say, given the behaviour of the iron filings, there must be a magnetic force present. However, to say that does

not mean the same as saying that there must exist magnetic force, full stop. The particular instance of magnetic force here actually exists. It might not have existed, but given the existence of certain other things, it could not have failed to. Understood this way, a close relationship between actuality and conditional necessity does not seem so troubling.

Another response would be to take the necessary connection involved in actuality to be epistemic, as opposed to physical or metaphysical necessity in the conditioned necessity case. So, e.g., the iron filings constitute evi- dence of magnetic force, but something else may have caused (i.e. causally necessitated) there to be a magnetic force. However, this approach would spell disaster for actuality. Things could only actually exist if there was actually perceived evidence for their existence. Again, this strikes me as overly idealist, even for Kant. This reading is suggested by the iron filings example. After all, no one wants to argue that the movement of the iron filings in any way necessitates the existence of a magnetic force. A clarifica- tion may help here: the view is not that the object of actual perception is always the cause or equivalent of the actual existence of an indirectly per- ceived thing. Rather, the object of the perception is taken to stand in some appropriate relation to the other object. E.g., we know the iron filings could not move without a cause. Science tells us that that cause is a magnetic force. So we conclude from the movement of the iron filings that there is an actual magnetic force. So yes, the actual perception is used as evidence for the conclusion that there is a magnetic force, but the crucial relation which ensures the actuality of the magnetic force is not that the iron filings provide evidence for the magnetic force (although they do), but that the laws of experience state that the filings and the force will be related in a certain way.

The notion of necessity we are left with is then explicated by Kant in terms of causal necessity. We know that this material necessity is connected to the universal laws of experience. In the present passage, this amounts to what appear to be three laws of physics.16 For Kant, certain physical principles are a priori, and these are amongst the conditions to which the concept of an object must conform if it is to refer to a possible object. An object has (conditional) necessary existence if it follows from a previous experience according to these laws of physics. But it is a mistake to talk here of necessarily existing objects. An important point is that Kant does not think that there could be such a thing as a necessary existent or a necessarily existing being. He indeed goes on to claim that this kind of conditional, causal necessity only regards the states of things, not the existence of things.

Now there is no existence that can be cognized as necessary under the condition of other given appearances, save the existence of effects from given causes, in accordance with laws of causality. It

is not, therefore, the existence of things (substances) that we can cognize to be necessary, but only the existence of their state; and this necessity of the existence of their state we can cognize only from other states, which are given in perception, in accordance with empirical laws of causality. (A227/B279)

The reason seems to be that we are dealing with causal necessity, a relation between causes and effects, so we must be dealing with states. This will depend on a claim about the relata of the causation relation; objects or states.

A restriction here to causal necessity seems misguided. First, the laws of mathematics as well as the laws of physics, according to Kant, guide the behaviour of objects in the world. So it seems reasonable to expect these conditional necessities to follow from mathematical as well as causal laws. It seems plausible to claim that nothing exists absolutely necessarily where this is a case of causal necessity, but once we have a richer notion of necessity in the picture, this may not be so straightforward. One might argue that the number 2 exists of mathematical necessity, and unconditionally so. Given the scope and importance of these issues to do with conditional necessity and abstract objects, I will discuss them in more depth once the main views have been outlined.

The relation between necessity and possible experience is brought out in the following way. Necessity is a matter of causal relations, and the causal law is an a priori condition on possible experience. So necessity is thereby a matter of determination by causal laws, which are a condition on experience.

It therefore follows that the criterion of necessity lies solely in the law of possible experience, the law that everything which happens is determined a priori through its cause in the [field of] appearance. We thus cognize the necessity only of those effects in nature the causes of which are given to us, and the character of necessity in existence extends no further than the field of pos- sible experience, and even in this field is not applicable to the existence of things as substances, since substances can never be viewed as empirical effects—that is, as happening and coming to be. Necessity concerns only the relations of appearances in con- formity with the dynamical law of causality and the possibility grounded upon it of inferring a priori from a given existence (a cause) to another existence (the effect). (A227-8/B279-80)

Again, the notion of necessity is restricted to the realm of experience, against the temptation to posit the existence of transcendent necessary beings such as God.

In terms of giving a clear exposition of Kant, the third principle of modal- ity concerning necessity is really intended by Kant to capture a notion of

conditional, causal necessity. However, below I show how a more general no- tion of necessity, mirroring the account of possibility (which is not restricted to causal possibility) can be taken from Kant, which yields a simpler view.