Within Tendai thought, original enlightenment, or hongaku, designates the insight that all beings and all phenomena are, in their very nature, already enlightened. Enlightenment is not regarded as something newly produced through effort, but as the fundamental reality—suchness—that is always fully present. The deluded mind is not a separate or inferior substance; it is original enlightenment itself, temporarily obscured by ignorance. From this perspective, practice does not manufacture Buddhahood but serves to reveal or manifest what has been present from the very beginning. Tendai interprets this in light of the teaching that each moment of consciousness contains the full reality of Buddhahood, so that the ordinary and the ultimate are never truly apart.

This vision naturally unfolds into a robust doctrine of universal Buddhahood. Every sentient being, without exception, possesses Buddha-nature and is inherently a Buddha, and there is no being ultimately excluded from this destiny. Tendai thinkers extend this universality even further, affirming that not only sentient beings but also insentient phenomena—plants, rocks, and the natural world—participate in Buddha-nature. Buddhas such as Śākyamuni or Amitābha are thus understood not as distant, separate entities but as manifestations of a single, all-pervasive Buddha-reality inherent in all things. The distinction between delusion and enlightenment, or between samsara and nirvana, is ultimately seen as illusory, for ordinary consciousness and Buddha-consciousness share the same ground.

From a practical standpoint, this does not render discipline and contemplation meaningless; rather, it recasts their purpose. Meditation, ethical conduct, devotion to the Lotus Sūtra, and esoteric rituals are understood as ways of actualizing or uncovering the enlightenment that is already complete. Tendai sometimes speaks of “acquired enlightenment” to describe this experiential realization, which removes obscurations and allows original enlightenment to shine forth. Thus, from one standpoint, enlightenment is originally accomplished; from another, it is something to be realized in lived experience. This dual vision allows spiritual practice to be both a path of transformation and a disclosure of what has always been true at the deepest level of being.