Tiantai, also known as the Tendai school in Japan, is a Mahayana Buddhist tradition that emerged in China during the 6th century. It is based on the teachings of the Lotus Sutra, which is considered the most important and comprehensive scripture in Mahayana Buddhism. Tiantai integrates all Buddhist teachings by placing the Lotus Sutra at the center and interpreting all other teachings in relation to it.

The core principle of Tiantai is the concept of "threefold truth," which states that all phenomena are ultimately empty, but also have temporary existence and a middle ground between the two. This concept is derived from the Lotus Sutra and serves as the basis for understanding the integration of all Buddhist teachings in Tiantai.

Tiantai teaches that the ultimate truth of emptiness is found in the Lotus Sutra, which is considered the final and most profound teaching of the Buddha. This truth is the ultimate goal of all Buddhist practices and teachings, and Tiantai sees all other teachings as skillful means to lead individuals towards this truth.

In Tiantai, the teachings of the Buddha are divided into five periods, with the Lotus Sutra being the final and most complete teaching. The earlier teachings, such as the Four Noble Truths and the Eightfold Path, are seen as preparatory teachings that lead individuals towards the ultimate truth of the Lotus Sutra.

Tiantai also integrates the teachings of other Mahayana schools, such as the Madhyamaka and Yogacara, by interpreting them in relation to the Lotus Sutra. For example, the Madhyamaka concept of emptiness is seen as the ultimate truth of the Lotus Sutra, while the Yogacara concept of the threefold nature of reality is seen as the temporary existence and middle ground between emptiness and temporary existence.

Furthermore, Tiantai incorporates the teachings of the Pure Land school by interpreting the Pure Land as a temporary existence that serves as a stepping stone towards the ultimate truth of the Lotus Sutra. This integration allows for a comprehensive understanding of the various teachings and practices within Mahayana Buddhism.

Overall, Tiantai integrates all Buddhist teachings by placing the Lotus Sutra at the center and interpreting all other teachings and practices in relation to it. This allows for a harmonious and comprehensive understanding of the Buddha's teachings, leading individuals towards the ultimate truth of emptiness and awakening.