Syntactic Theory
Passive
Properties of the Active - Passive Relation
Consider again the following example:
(1) a. The flea bit the dog. b. The dog was bitten (by the flea).
The sentence in (1a) is the active sentence and (1b) is its passive counterpart. What is the relationship between these two constructions?
1. The subject of the passive sentence corresponds to the direct object (first NP complement) of the active sentence.
2. The participant denoted by the subject of the active, if expressed at all, is referred to by the object of the preposition by.
3. The valence requirements of active and passive sentences are identical otherwise, as illustrated in the following examples. The active form handed requires an NP and a PP[to] as its complements, and the passive handed still requires the PP complement:
(2) a. Matt handed the letter to Tom. b. *Matt handed the letter. c. *Matt handed to Tom. (3) a. The letter was handed to Tom (by Matt). b. *The letter was handed (by Matt).
4. As shown in the Introduction, the semantic roles of the active and passive sentence are the same.
5. The morphology of the passive form of the verb ('passive participle') is identical to that of the past participle.
6. The passive participle is usually preceded by a form of be.
Note: From property (2) above it follows that sentences with intransitive verbs, like (4a), normally do not have passive counterparts, as in (4b) (examples taken from Sag, Wasow, Bender 2003, p. 312).
(4) a. The patient died. b. *The patient was died (by the doctor). c. *The doctor died the patient.

In the next section, you will learn how these syntactic and semantic relationships between active and passive forms are captured systematically in a lexical rule, the Passive Lexcial Rule. To get there, click here.