If oneicity was in the dictionary (give us time…we’ll get those Webster guys on board),
it might appear like this:

one•i•ci•ty \wuhn-’i-si-tee\ 
–noun 
1. singular purpose, unity, oneness
2. knowing and being known, transparency

It is a word we created that is like:

authenticity: the quality of being authentic; genuineness

electricity: a state or feeling of excitement, tension, anticipation

elasticity: the quality of being flexible, resilience, adaptability; buoyancy

felicity: a state of being happy, especially in a high degree; bliss

publicity: extensive mention in the news media or by word of mouth or other means of communication

simplicity: freedom from deceit or guile; sincerity, freedom from complexity, intricacy, or division into part

synchronicity: the state or fact of being synchronous or simultaneous