Next: 6.2 Finite or Infinite? Up: 6. Actuality Previous: 6. Actuality
We have to start somewhere, however, so let us hypothetically postulate `actual particulars' as one of the more basic kinds of particular things in the natural world. The following sections will consist of the exploration of the consequences of this hypothesis, and the final section of this chapter will consider what in the physical world we know can be described as an actual particular.
There are many different things we can mean when we say that `something actually exists'. Stoothoff , for example, distinguishes the actualities of continuants (those things which continue), occurrents (those things which occur), and attributes (those things which are properties of other things). In everyday language, `actual' can qualify a very wide range of particulars, abstract as well as concrete. We will see, for example, the confusion that can be caused by the use of the term `actual infinities' in mathematics.
The second sense is much wider, and with it one can even say ``the actual potentialities'' or ``the actual range of possibilities''. By these expressions we do not mean that potentialities are actual, or that we are confusing possibilities and actualities, but that we are talking about ``the present potentialities'' etc. This second meaning of `actual' is practically synonymous with `present'. The meaning of `present', `past' and other tensed descriptions will be discussed in the next chapter (there I will argue that they can be defined in terms of the distinction between possibilities and actualities in the first sense).
We might think to provisionally define actuality in the third sense: that x is actual if and only if x either acts, or undergoes change, or both, as Geach  suggests. This definition is intended to exclude such things as numbers and mathematical functions, as numbers and functions (even when called `wave functions') do not appear to either act or undergo change in any real sense. Geach's definition is intended to include such things as objects, atoms, people, etc. For the present purposes, however, his definition is too broad. This is because if a thing is to act or to undergo change, it must have been possible for it to so act or change. Any explanation of the ability to act or change must ascribe the possibility of acting or undergoing change to the thing itself, and thus there is a sense in which the thing we thought actual in fact has possibilities ascribed to it. If we contrast `possibilities' to `actualities', then we would have a complicated mixture of opposing notions in those things which we thought were actual in the simplest sense.
This is quite a selective definition of `actuality', as will be seen. The phrase `fully determinate' means that all the characteristics of the particular (given its existence) are definite, fixed and precise. By being fixed, is not meant fixed by us, or fixed or determined by the causal predecessors of this particular. Rather, by `determinate' as against perhaps `determined', is meant that all the characteristics of the thing are definite in themselves. By `simple' is intended that these things are not really aggregates of some more basic particulars, for then `pure actuality' would be intended to refer to those particular things.
It is important here to distinguish the meaning of `determinate' from that of `determined'. If something is determined, then its characteristics can be derived from states of affairs which precede it in time. There would then be something like a physical law which allows the determination of the thing given some past history. If something is `determined', therefore, we are stating a relation between that thing and other previous things. If something is determinate, however, then we are stating a property just of that thing. We are saying that its characteristics are definite and fixed, and we are not making any reference to other things either alongside it, or in its past.
Note, also, that defining pure actualities as the fully-determinate particulars in the world does not imply that there cannot be other kinds of particular things. It only means that they cannot be fully determinate, not purely and fully actual. It remains to be seen what they might be: chapter 9 will suggest some candidates for particulars which are not purely actual.
The only change possible with respect to them is that they start existing, or that they stop existing -- only their creation or their destruction. The determinate nature of actualities does not prejudge the question of whether or not they can start or stop existing. This is because `determinate' means that, if it exists, the characteristics of an actual particular are immutable. If it does not exist, then there is no such actuality, and it is meaningless to talk about its characteristics, for there is no referent for any name we may have. We can only talk of certain characteristics in themselves, without any particular reference being implied. From this we can conclude that no actuality can be the cause of its own creation, as it cannot be there to do the job. More subtly, a fully actual particular cannot be the cause of its own destruction, because there are no un-actualised possibilities in the constitution of an actuality, and hence, in particular, no possibility for its ceasing to exist. These two conclusions do not prohibit the creation or destruction of actualities -- their becoming or perishing -- by some means or other. They only indicate that the causes must be elsewhere than in the nature of the actualities themselves.
Before we consider purely actual particulars in more detail, however, it is necessary to decide whether actualities are all finite, or whether they can be infinite.
Next: 6.2 Finite or Infinite? Up: 6. Actuality Previous: 6. Actuality Prof Ian Thompson