Here are two clauses joined by a relative pronoun (that) which is the subject of the secind clause but incidentally dropped. ‘that’ refers to the subject of the main clause ‘what’’ which is singular. So you need a singular verb ‘is’. In that case, replace plural noun ‘principles’ by singular noun ‘guiding principle’. Say:
What makes each of us unique (that) is our guiding principle
Our guiding principle is what makes each of us unique.
do you mean we can't make a sentence with phrasal plural 'our principles' in this case.
***** NOT A TEACHER *****
(1) Some experts say that "what" is always singular ("The thing that").
So your second sentence would be correct.
I don't understand if "what makes each of us unique is our principles" is true , so I can be sure that "It is our principles" is also true, isn't it?
I think it should be "what makes each of us unique is our principle"
Can you explain me more about "principle" , "principles" and the influence to the choice of "is" or "are" in this case please. Thanks.
Your use of "true" is incorrect. You mean "correct".I don't understand if "what makes each of us unique is our principles" is true , so I can be sure that "It is our principles" is also true, isn't it?
The similarity with NPs can be further seen in the fact that certain nominal relatives exhibit number contrast:
Singular: [What we need] is a plan
Plural: [What we need] are new ideas