The Sanlun school, also known as the Three Treatise school, is a Chinese Madhyamaka school that emerged during the Tang dynasty in China. This school is based on the teachings of the Indian philosopher Nagarjuna and his Madhyamaka philosophy. The Sanlun school emphasizes the concept of emptiness and the relationship between ultimate reality and conventional reality.

According to the Sanlun school, ultimate reality is the true nature of all things, which is empty of inherent existence. This means that all phenomena, including ourselves, are ultimately empty of any independent or inherent existence. This emptiness is not a nothingness, but rather a lack of inherent existence or essence. It is the ultimate truth of all things and the ultimate reality that underlies all conventional phenomena.

On the other hand, conventional reality refers to the world we perceive and experience through our senses. This includes all the phenomena that we see, hear, touch, taste, and smell. The Sanlun school views conventional reality as being dependent on ultimate reality. In other words, conventional reality is a manifestation of ultimate reality, but it is not the ultimate truth itself.

The relationship between ultimate reality and conventional reality is often described in terms of two truths – the ultimate truth and the conventional truth. The ultimate truth is the true nature of all things, while the conventional truth is the world of appearances and concepts. The Sanlun school teaches that these two truths are not separate or contradictory, but rather they complement each other. Ultimate reality is the foundation of conventional reality, and conventional reality is the manifestation of ultimate reality.

The Sanlun school also emphasizes the concept of dependent origination, which states that all phenomena arise and exist in dependence on other phenomena. This means that conventional reality is dependent on ultimate reality, and that the existence of conventional phenomena is dependent on the emptiness of ultimate reality. In other words, without the emptiness of ultimate reality, conventional reality would not exist.

In conclusion, the Sanlun school views the relationship between ultimate reality and conventional reality as one of dependence and complementarity. Ultimate reality is the true nature of all things, while conventional reality is the world of appearances and concepts that arises in dependence on ultimate reality. By understanding the interdependence of these two truths, one can gain a deeper understanding of the nature of reality and ultimately achieve enlightenment.