sine qua non
/ˌsɪni kwɑː ˈnəʊn,ˌsʌɪni kweɪ ˈnɒn/

noun

an essential condition; a thing that is absolutely necessary.
“grammar and usage are the sine qua non of language teaching and learning”

Man, the communicator; relationships has the potential of evolution beyond oneself – this is the pathway to the Multi-Mind Organism.