An object which we have formerly seen in conjunction with others, and which we do not conceive to have any property that is not common to many, will not be regarded by us for so long, as an object which we conceive to have some property peculiar to itself.
Proof .-- As soon as we conceive an object which we have seen in conjunction with others, we at once remember those others (II.
xviii.

and note), and thus we pass forthwith from the contemplation of one object to the contemplation of another object.

And this is the case with the object, which we conceive to have no property that is not common to many.

For we thereupon assume that we are regarding therein nothing, which we have not before seen in conjunction with other objects.

But when we suppose that we conceive an object something special, which we have never seen before, we must needs say that the mind, while regarding that object, has in itself nothing which it can fall to regarding instead thereof; therefore it is determined to the contemplation of that object only.