So I was reading the urban dictionary for the definition of the term 'LibLabCon', and the entry seemed grammatically correct:
LibLabCon is a phrase used by Britons who hold the belief that there is no real discernable differences between the mainstream political parties in Britain, and that the country is thus technically a one-party state.
Fair enough. No big deal. However, I noticed something weird in the relative clause that modified the noun phrase 'the belief'. The auxiliary verb 'be' didn't agree with the plural 'differences' in the clause's noun phrase ('no real discernable differences').
Is it grammatically correct to use the singular 'is', or should it be the plural 'are'? I am curious as to what governs the auxiliary verb in this relative clause so that I can answer this question. I thought it could be three things:
The relative pronoun 'that'. This is because I have seen 'that' govern the auxiliary before (e.g. 'the people that are working hard will earn more' and 'the person that works the hardest will earn the most'). The antecedent 'belief' is singular.
The grammatical expletive/dummy subject (or pronoun, whatever it's called). I believe that this would mean that the 'is' is correct.
The noun phrase (this is what I believe actually governs it). Due to the fact that 'differences' is plural, the auxiliary verb 'are' would be correct instead of 'is'.
As you can tell, I'm a little confused. Any help would be much appreciated!