I just realized through inner cerebration the link between passive voice and present complete tense. Consider the following sentence: I have finished my homework. A standard inversion yields: I have my homework finished. If this is not yet revealing to you, let me push it further and derive the following: I have that my homework is finished. What we see here is that the past participle "finished" here can take either the role of a subdued verb or that of an adjective, despite that the adjective must be one of active origin. I think it’s etiomologically sound to prefer the adjectivic interpretation of past participles, because romance languages seem to prefer the syntactical structure of having something acted upon. Perhaps it is ingrained in the philosophy that past actions become part of oneself. It also reinforces primitive meaning of the word have as a verb of possession, rather than as an auxilliary helping verb that modern linguists created for pedagogical convenience.