I can both see and interact with mine, anyone who can reach a deep meditative state has expiernced it.
It is fromt his expiernce, and sharing it with others capable of reaching the mental state, it seems clear to me that there is one other such second mind, and that we interact with it. Since this other mind and my own see eachother as seperate (or atleast I see it as seperate) it seems clear to me they are not perceived as one, once one is able to "see" it at all (normally you arent aware of it, in which case I suppose you can say they are seen as one during normal operations :) )