There are of course no merely negative relations in nature, and exclusion is not the mere negative of inclusion, though the two relations are contraries.

Both relations are concerned solely with events, and exclusion is capable of logical definition in terms of inclusion.
[10] Cf.

note on 'significance,' pp.

197, 198.
[11] Cf.Ch.III, pp.

51 et seq.
Perhaps the most obvious exhibition of significance is to be found in our knowledge of the geometrical character of events inside an opaque material object.