Rav Shmariah mentions in detail the application of this theory to leprosy, emissions and births. It is akin to certain states of depression since it is characterized by a feeling of helplessness and lack of activity. It follows that perhaps other activities are also predetermined. Maybe we can't avoid them happening. Thus our freedom in the sphere of intimacy is challenged.
Human birth is a purely animal process.
It is totally physical. Again the idea that freedom is there is attacked. The purification ceremony for the person in contact with a dead person emphasizes mans spirit. By sprinkling this on the person who was in contact with the dead we 'purify' him since we remind him that he not only has seen death but is reminded of the eternal soul. But the people involved with the sprinkling become impure.