Yoga is a vision for a harmonious future for humanity. It is an "stage" i.e. a state of mind not "system".

An open mind leaves a chance for someone to drop a worthwhile thought in it.

Insubordination may only be the evidence of a strong mind.

Iron rusts from disuse; water loses its purity from stagnation... even so does inaction sap the vigor of the mind.

Knowledge of the past and of the places of the earth is the ornament and food of the mind of man.

Culture of the mind must be subservient to the heart.