There are countless special senses in Nature.
Bats can see moths in the darkness with their ears.
Migrating birds can see the magnetic fields generated by the poles of the earth,
like geographic lines on a global map.
Certain fish can see the shapes of objects in the water by similar means,
some magnetic, some by the effect of their movement on the echoes of moving water.
Some water predators see their pray by sensing the electricity generated
by it operating its muscles.
Blind people can see the wall marking the edge of a swimming pool by
feeling the water becoming harder to move through.
Senses can be identified, defined as distinct, and named,
only if we can identify the organs that produce the resulting perception,
and only if the process of evolution making them distinct is complete.
Our brain is young and highly variable.
Most blind people do not see the edge of the swimming pool,
but many of them do.
We have many structures still evolving.
It is convenient to digitize the language and talk about having exactly five senses.
It is misleading to compare the vision of blind people to that of the bat,
not because one uses the sense of hearing and the other that of touch,
but because the vision qualities of the bat are distinct and perfected.
As a side note, it is implied by the D. Postulate,
applied to the development of vocabulary,
that words in the language will become distinct and well
separated, much like species and their individual attributes.
As the time scale is much denser in this case,
the language senses have in fact been perfected long ago.
02 - Variations Under Nature
