Some say that we have a change when a thing has a property at one time that it does not have at another. However, that either doesn’t tell us what change in itself is - it just tells us when we typically recognize there to have been a change - or it is a circular and so tells us nothing. For it appeals to a change in temporal properties. When a thing goes from being present to being past, it has already changed – changed from being present to being past. So if we are trying to get a handle on what change itself is, we can’t appeal to another change as then we are trying to explain change with change, which gets us nowhere.

So what, then, is change in itself? Well, it seems to me that a good place to start is to think about how we detect it (even though it is an egregious mistake to confuse one's detection of something with the thing itself).

I suggest that we first detect change by way of sensation. For after all, it can seem to us that something has changed even when we cannot identify 'what' has changed. Just as, by analogy, we can sometimes hear something, yet not know what is producing the sound, or feel the texture of something yet not know what was producing it in us, or smell something yet not be able to locate the source of the smell. And of course, we can also get the impression a change has occurred when no change has occurred. This too lends weight to sensationalism about how we detect change, for our sensation of change does not itself constitute the change it is a sensation of, and thus it is to be expected that we may sometimes have the sensation in the absence of any change.

Typically anyway, we have the sensation of change and then notice what seems to have caused that sensation in us, and identify that as ‘the change’, in much the same way as we might call something that caused us pain, ‘painful’, or something that caused a loud noise 'noisy' or whatever. So we identify the change with what seemed to us to cause in us the change sensation.

If this is correct, then does this tell us anything about what change itself is?

I think so, thanks to a simple argument of George Berkeley’s. Sensations, argues Berkeley, give us insight into reality by resembling parts of it. That is, there must be some resemblance between our sensations of reality and reality itself, else our sensations will simply not qualify as being ‘of’ reality at all.

If that is correct, then the sensation of change must resemble actual change, else it would not be ‘of’ change at all.

Next step: sensations can resemble sensations and nothing else. Sights resemble sights, sounds resemble sounds, smells resemble smells and so on. Thus, as the sensation of change resembles actual change, and a sensation can only resemble another sensation, change itself can now be concluded to be made of a sensation.

Next step: sensations can exist in minds and nowhere else. Their essence is to be sensed (as Berkeley put it “Their esse is percipi”).

But the changes that our sensations of change give us insight into exist outside of our minds. Indeed, there are ‘the’ actual changes, and then there are our sensations of change (as we all recognize, for we recognize that the fact it seemed to us that a change occurred is not decisive evidence that one did occur). So it seems that the actual changes that our sensations give us insight into are unitary, indeed they are part of the unity we call ‘external reality’ or (misleadingly) the ‘objective world’. (By saying they are unitary, I do not mean there is just one change; I mean rather that there are 'the changes' that occur in the unitary external world).

From this it follows that change itself is the sensation of a single mind. That which has caused the sensation in question can then be identified with that which has changed, just as that which has caused an auditory sensation is that which was heard.