As I am studying the theory of two truths, I feel it was emerged for the clarification of the truth that Buddha mentioned in his teachings. We all know that Buddhism is based on the truth. Sometimes, we also use the word "Dhamma" for the truth according to its content. Even though Buddha did not specifically teach the theory of truth, it corresponds with his teachings. When a nun Vajira was asked about being, she gave a simile of a vehicle. Just like an assemblage of parts is called a vehicle, the presence of the five aggregates of clings is called a being. To me, we see the theory of two truth. There is a conventional truth because a vehicle that we commute with everyday for our convenience. We cannot say that we came to work in the collections of parts. Conventionally, we use the term vehicle because it is agreed by the conventional world. In that sense, it is a truth but only convention.
On the other hand, we look into the ultimate truth as we see nothing but combination of four elements in the vehicle which are irreducible. They are namely earth, water, fire and air. Similarly in a person we see an ever changing of the five aggregates which are the ultimate truth. We cannot say that this five aggregates are talking to that five aggregates. In conventional term, we use the concept such as "he, she, we, they" or a person or by a name. It is important to note that they are simply concepts but not ultimate realities because they are relative and thus reducible, but ultimate truths are not. There are four ultimate truths: citta, cetasika, rupa and Nibbana. The former three are conditional and latter one is unconditional.
Therefore, I believe that the theory of two truth is to make Dhamma easy to understand, so that practitioners can witness and realize the reality as it is.
