The bright and the dark paths of the world are verily thought to be eternal; by the one (the bright path) a man goes not to return and by the other (the dark path) he returns.
In simple words
Krishna summarizes: "These two paths — the bright and the dark — have existed since the beginning. One leads to no return. The other leads back to this world."
Word-by-word meanings
शुक्लकृष्णेbright and darkगती(two) pathsहिverilyएतेtheseजगतःof the worldशाश्वतेeternalमतेare thoughtएकयाby oneयाति(he) goesअनावृत्तिम्to nonreturnअन्ययाby anotherआवर्तते(he) returnsपुनःagain
8.26 शुक्लकृष्णे bright and dark? गती (two) paths? हि verily? एते these? जगतः of the world? शाश्वते eternal? मते are thought? एकया by one? याति (he) goes? अनावृत्तिम् to nonreturn? अन्यया by another? आवर्तते (he) returns? पुनः again.Commentary The bright path is the path to the gods taken by the devotees. The dark path is of the manes taken by those who perform sacrifices or charitable acts with the expectation of rewards. These two paths are not open to the whole world. The bright path is open to the devotees and the dark one to those who are devoted to the rituals. These paths are as eternal as the Samsara.World here means devotees or people devoted to ritual.Pitriloka or Chandraloka is Svarga or heaven.
Contemporary scholarly and practical interpretations for modern seekers.
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
Modern
The two paths previously mentioned—the path of the devas and the path of the ancestors—are here referred to respectively as the path of light and the path of darkness. They have been renamed according to the nature of their respective destinations. The first path leads the seeker to the highest summit of ascension, while the other path consequently leads into the abyss of descent. These two paths may be understood respectively as the path of liberation and the path of worldly existence.
In every generation of humanity, there exist two paths or ways of living: the material and the spiritual. According to materialists, human needs are merely food, clothing, and shelter. In their view, the ultimate purpose of life is to satisfy the excitations of body and mind through the enjoyment of sensory pleasures. This alone brings them contentment. They have neither interest nor inclination toward any higher and divine ideal. However, those of discriminating wisdom who walk the path of spirituality are not seduced by attractive objects that appear before them. Their intellect, like the flame of fire, is ever upward-ascending, seeking and delighting in the discovery of higher and supreme goals amidst the surface of ordinary existence.
Lord Sri Krishna declares that both these paths are eternal, and since time immemorial, people of two different natures have walked upon them. In the broader sense, the combined form of both constitutes the world. Yet the principle of Vedanta teaches that the individual soul can be freed from the suffering of worldly existence. This is the direct experience of the sages.
When contemplated from the perspective of a spiritual seeker, this verse reveals guidance for becoming a successful yogi. Sometimes during the period of practice, due to the outward-turning tendency of the mind, the seeker becomes attracted to sensory objects and becomes attached to them. In such moments, there is no need for us to condemn ourselves, nor to be bewildered in wonder. The Lord makes clear that within the human mind, the eternal conflict between the aspiration for higher life and attraction toward lower life has been raging since time without beginning. Through patience and perseverance, we can gain victory over the lower tendencies.
What then is the certain fruit of knowing these two paths and their eternal nature?