Others can only have been grasped by him after he had reached a relatively high stage of human development.
(Others; can only have been grasped; by him; T:after he had reached a relatively high stage of human development) (he; had reached; a relatively high stage of human development)
Others he
can only have been grasped had reached
by him T:after he had reached a relatively high stage of human development
a relatively high stage of human development