The Principle of Temporal Sequence (PTS) was proposed by linguist Tai in 1985. The principle states: “The relative word order between syntactic units is determined by the temporal order of the states they represent in the conceptual world.” The PTS, put in another way, states that events represented by linguistic units are arrayed in their logical order in the physical world, that is, what happens first in the physical world is encoded first in a sentence. The PTS is the generalization of several facts of Chinese word order.The principle controls the order of two clauses that are conjoined by temporal adverbs, such as ‘zài’ (then), ‘jiù’ (as soon as), and ‘cái’ (then, only then), for example:
Xǐ le shǒu, zài chī fàn.
(First wash hands, then eat.)
*Zài chī fàn, xǐ le shǒu.
Wǒmen yī xià kè, tā jiù lái le.
(As soon as the class was over, he came.)
*Tā jiù lái le, wǒmen yī xià kè.
Mǎi le jīpiào, cáinéng shàng fēijī.
(Only after buying a plane ticket, can you board the plane.)
*Cáinéng shàng fēijī, mǎi le jīpiào.
Each clause in the above sentences describes an event. The event named by the first clause happens earlier than the event named by the second clause. Hence, syntactically, the first clause precedes the second. The reverse order results in ungrammatical sentences.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.