Two forces have been working side by side in parallel lines.
The one says "I", the other says "not I".
Their manifestation is not only in man but in animals, not only in animals but in the smallest worms. …
… throughout creation these two forces are working side by side; where you find the one, you find the other too.
The one is selfishness, the other is unselfishness.
The one is acquisition, the other is renunciation.
The one takes, the other gives.
From the lowest to the highest, the whole universe is the playground of these two forces.
It does not require any demonstration; it is obvious to all.
- Swami Vivekananda,
Practical Vedanta IV,