PHIL2109 Contemporary Metaphysics
Week 4: Qualitative Change

Qualitative change

  1. Consider a banana that changes from being green to being yellow. It has undergone a qualitative change: it has changed from having a certain quality at one time (being green) to not having that quality at a later time. It has also changed from not having a certain quality at one time (being yellow) to having that quality at a later time. Either such change counts as a qualitative change.
  2. What is a quality? For present purposes it is an intrinsic (or non-relational) property, as opposed to an extrinsic (or relational) property. Being green is an intrinsic (non-relational) property; having a nephew is an extrinsic (relational) property.

    If something changes in whether or not it has an extrinsic (relational) property this does not count as a qualitative change; it is sometimes called a Cambridge change.

  3. There seems to be a distinction here between two kinds of property. If so, can we characterize it?

A non-problem

  1. The possibility of qualitative change might seem to be ruled out by Leibniz's law. Leibniz's law says this:

    So according to Leibniz's law, it is not possible for a banana to both have and not have the property of being green, so it cannot change from being green to not being green.

  2. There is an obvious response: “Sure, the banana cannot both have and not have the property of being green at the same time, but it can have it at one time and not have it at another time.”

    We can see that Leibniz's law allows this by making explicit its implicit reference to time:

  3. To avoid concerns about grammaticality, we should understand the claims in this formulation tenselessly. Here are tensed and untensed ways of making the same claim:

    We seem to be able to make sense of this second way of talking. Perhaps it requires thinking of ourselves as commentating on the world from a point of view outside space and time.

    (Lowe claims that we use tenseless language when making mathematical claims. Is he right?)

  4. This tenseless way of talking seems to assume temporal realism, according to which all times are equally real, and thus equally available to be referred to. According to presentism, this is not the case: only the present time is real.

    Here is an argument that if presentism is true then there is no qualitative change (and so nothing to be explained): If presentism is true, then the only sentences of the form ‘x has p at t’ or ‘x does not have p at t’ which are true are those for which ‘t’ refers to the present time. So the only sentences of the form ‘x has p at t but x does not have p at t'’ which are true are those for which both ‘t’ and ‘t'’ refer to the present time. But no such sentence can be true. So it is never true to say ‘x has p at t but x does not have p at t'’. So there is no qualitative change. What should we make of this?

  5. The debate between presentism and temporal realism mirrors a debate between actualism and modal realism (more about this later in the course).

A problem

  1. The problem of qualitative change is this: trying to explain what it is for something to undergo qualitative change - what it is to change from having an intrisic property (i.e. quality) p at time t to not having p at a later time t'. It is also called the problem of temporary intrinsics.
  2. This is a different kind of problem from the one posed by the puzzle of the ship of Theseus. In the latter case we feel ourselves wanting to say two seemingly incompatible things; in the present case we feel ourselves not wanting to say anything.
  3. Contemporary discussion has tended to involve issues in the philosophy of language, seeking to clarify what kind of thing we are saying when we say, ‘x has p at t’. Are we saying that a certain thing has a certain property, or that a certain two things stand in a certain 2-place relation, or that a certain three things stand in a certain 3-place relation, or something else? That is, what is the logical form of the sentence ‘x has p at t’? Or, how should we formalize this sentence in a formal language: ‘Pa’, or ‘Pab’, or ‘Pabc’, or some other way?

Some accounts

  1. There are at least four accounts that we should consider:
  2. (x) has (p at t). When we say ‘x has p at t’ we are saying that a certain thing stands in a certain 2-place relation to a certain property, and we are using ‘at t’ to specify which property it is. For x to change from being p at t to not being p at t' is for x to stand in the having relation to the property (p at t) but not the property (p at t').
  3. (x at t) has (p). When we say ‘x has p at t’ we are saying that a certain thing stands in a certain 2-place relation to a certain property, and we are using ‘at t’ to specify which thing it is. For x to change from being p at t to not being p at t' is for one thing (x at t) to stand in the having relation to the property p while another thing (x at t') does not.
  4. (x) has at t (p). When we say ‘x has p at t’ we are saying that a certain thing stands in a certain 2-place relation to a certain property, and we are using ‘at t’ to specify which relation it is. For x to change from being p at t to not being p at t' is for x to stand in one relation to p (having at t) but not stand in another relation to p (having at t').
  5. (x) has (p) (at t). When we say ‘x has p at t’ we are saying that a certain thing stands in a certain 3-place relation to a certain property and a certain time, and we are using ‘at t’ to specify which time it is. For x to change from being p at t to not being p at t' is for x to stand in the having relation to p and one time (t) but not stand in the having relation to p and another time (t').
  6. A concern: might we have the same debate about ‘a is between b and c.’? Is there a significant issue in this case? If not, is there a significant issue in the case of ‘x has p at t’?

Temporal parts

  1. The second of the accounts above, a currently very popular one, takes it that persisting things (i.e. things that exist for an interval of time, such as chairs) have temporal parts.
  2. The following are typically said of temporal parts:
  3. Are there such things as temporal parts? Here are some arguments that there are:
  4. Here are some arguments that there are not: