Chemistry ceases to improve when one element is found from which all others are deductible. Physics ceases to progress when one force is found of which all others are manifestations. So religion ceases to progress when unity is reached, which is the case with Hinduism.
Social progress takes effect through the replacement of all institutions by new ones; and since every institution involves the recognition of the duty of conforming to it, progress must involve the repudiation of an established duty at every step.