There is nothing to show that he may not reach, in his psychical and social development, a stage at which the conditions of his life will be still far from satisfactory, and beyond which he will find it impossible to progress.

This is a question of fact which no willing on man's part can alter.

It is a question bearing on the mystery of life.
Enough has been said to show that the Progress of humanity belongs to the same order of ideas as Providence or personal immortality.

It is true or it is false, and like them it cannot be proved either true or false.

Belief in it is an act of faith.
The idea of human Progress then is a theory which involves a synthesis of the past and a prophecy of the future.