For those verbs that can be applied to oneself (directly, indirectly or mutually*) it is both, unless the context restricts the meaning to only one sense. Other verbs make sense only in one of the two ways... or neither, in which case they are said to have a neutral sense (they denote a state rather than an action).So how do we know which verbs are Middle with Passive sense or Middle with Active sense? Memorization? I'm guessing there's a chart somewhere...
In case it is not evident, the sense has to do with the meaning, whereas the voice with the grammar.
It would depend on the usage and where the focus is, on the end result, the action itself or on who is carrying out (or suffering) the action.While I have you then, let me ask you something I have always wondered about: I sometimes leaned towards defining Middle Voice using the word become, as in to "become loosed from," to distinguish true Middle voice from to "be loosed from" which reads like passive, and "loose myself from" which reads more like active. What do you think?
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* two people kissing each other for example. :-)