The further direction of measurement inevitably interpenetrates our tridimensional universe. That further direction of measurement is imperceptible to our sensorial apparatus, but our minds (plural purely conventional), being imperceptible, presumably function along that dimension.
Apparently confined by our three directions of measurement, we think we only communicate along those three, so we shout at one another, kick or kiss one another, look at one another with or without magnifying glasses. Our contacts are exclusively superficial, and we judge one another, react to one another by liking and disliking, in a crude manner based on this contact that is confined to our three superficial dimensions only of approach. Never by this method can we know more than the surface of one another, or of anything, for never can we make contact otherwise than by a surface touching a surface.
Meanwhile our minds, functioning in a further direction of measurement which cannot but interpenetrate the three that our senses enable us to know, are in permanent contact inevitably unfettered by our temporal and spatial limitations of interpretation.
Our minds, which are mind itself interpreted as 'us', are ultimately one, but in so far as differentiation emanating from 'us' segregates them 'around' us they fulfil the function of communication by the mere impulsion of desire on our part for such communication, and without the application of any cumbrous technique such as our dualistic system of words.
How strange that we do not seem to know this! Not knowing it, we do not consciously use it. Yet it certainly takes place 'behind our backs'. Why do we not use it? Some of us do without knowing it; others use it deliberately. Does it require an elaborate technique? My guess is that it is just about as difficult as riding a bicycle. But it surely cannot be used except by those who know, understand, realise that it is there to be used.
Having realised that much, it is barely a step to the realisation that just a little further from the periphery - our minds are all one and the same mind, and that there is nothing else.
'To one who has discovered his real nature, how can there be anywhere or anything separate from it?' (Huang Po, Wan Ling Record, 43.)