Part of the problem is that parts of the verb be have two distinct functions in English. One of their uses is copulative (stop sniggering at the back there), they join a subject and a complement (which is usually a noun or an adjective). Examples: She's a doctor. He's delirious.
The other use is as an auxilary verb making some compound verb forms, the progressive and passive forms. (He was running hard because he was being chased.)

In some sentences it is not clear whether we have copulative be followed by an adjective or auxiliary be followed by the third form of the verb. For example: The paper was torn. Is torn here part of the verb tear (Somebody tore the paper) or an adjective describing the state of the paper? Only the context can tell us which.

Bingley

Bingley