The semantic range of "to be"

Don Carson discusses several meanings for the linking verb "to be". He lists

1. Identity
2. Attribute
3. Cause
4. Resemblance
5. Fulfilment

Examples of these 5

1. A cat is an animal
2. The coat is leather
3. Listening is wisdom
4. People are sheep
5. That is what I said would happen

We can expand these sentences to restrict the semantic range of "is" and remove potential ambiguity by modifying the verb.

1. The cat belongs to the group animal
2. The coat is made of leather
3. Listening makes a person wise
4. People behave like sheep
5. This event corresponds to what I said would happen

Note that Identity is not always Equivalence. Equivalence is a special case of Identity where the subject and object can be interchanged such as "Clark Kent is Superman" or "aubergines are eggplants".

A 6th category (or perhaps a special case of "Attribute") is "Temporal/ Spatial," "the coat is on the floor."

Identity and Attribute can be essential (always belonging to the subject) or incidental (happening to belong to the subject).

Carson discusses this using the Greek verb (eimi) which appears to have a similar semantic range to English. His examples from the Bible are

1. Is the law sin? (Rom 7:7)
2. No one is good except God alone. (Mar 10:18)
3. To be carnally minded is death (Rom 8:6)
4. The tongue is a fire. (Jam 3:6)
5. This is what was spoken by the prophet (Act 2:16)

The context usually makes the meaning of "to be" clear, but discussion is needed about what is meant when there is ambiguity. Disputable or ambiguous passages include "this is my body" and "the Word was God".