The existence of a physical object manifests itself in its meetings — or, as it is frequently said, its interactions — with others. Through them it comes into appearance. From its effects on them, their changes induced by it, its own properties — and hence its existence — are deducible.

Some of these encounters may alterate the thing to such a degree that it does not stay the same thing. Maybe it splits into several others; or it fuses with another to form a new one; or it is absorbed by the other; maybe it even disappears completely, dissipating into some radiation or so (though this can be understood as consisting of kind of — somewhat curious — objects, too).

But normally contacts with other things do not change an object too seriously; so it does not only stay the same afterwards, but also between these contacts. At least, it is supposed to do so; strictly speaking, its existence between its interactions — and that is without them — cannot be proved and so remains vague.