Kinds of Impenetrability

Faced with the conflict between our intuition that no two things ever share a place at a time and these counterexamples to it, philosophers usually try to find a happy medium between sticking with the original intuition and rejecting all of its counterexamples or giving up the whole intuition and accepting all the counterexamples. Some counterexamples might be rejected on conceptual grounds : one may deny for instance that absolute space is in the same place that the entities located therein on the ground that absolute space is not itself located. One may also reject the distinct existence of some of the entities put forward in the examples : determinable properties might be nothing else than boolean combinations of determinate ones, spots on a screen may be just four dimensional worms whose passing through each other is a matter of part sharing rather than compenetration, etc. But as long as the conceivability of at least one counterexample is granted, the impenetrability intuition has to be weake- ned. To this end, one can weaken either the modal force of the impenetrability intuition or its scope. One may claim for instance that things are impenetrable in our world, but grant that the remaining counterexample refers to genuine metaphysical possibilities (although not natural ones). On the other hand, on may claim that the impenetrability intuition does not bear on every entity in the outside world, but only on some of them. Locke, famously, did not want to give up the metaphysical necessity of impenetrability, but agreed to restrict it to entities of the same kind.4 One other way to restrict the scope of the intuition of impenetrability is to claim that only independent entities (substances, or things proper) are impenetrable , or that only material entities are.