Conspectus v. Prospectus

Being awake at this odd and borderline profligate hour, I thought, "what better to do now than another word analysis?" So I scrolled through my interminable list of old DD wotds that I haven't yet looked at in the last 5 months and stumbled upon "conspectus". And I thought, what an odd word. Looks like prospectus. Defined like prospectus. Smells like prospectus. What's the difference? Why would we need this word.

Conspectus (DD definition links)
Prospectus

Well, etymologically, both derive from the same Latin root, specere meaning "to look", so the only difference here is the prefix of con (with, together or in association) and pro (normally for or favor, but more likely here, acting in the place of). So, how does this small derivation devolve into a formal summary of a general subject versus a brochure or document describing a specific proposed business venture, including a contract for goods or services and including education? They both are written accumulations of information. The issues appear to be the depth of the subject against the degree of review of the information intended. A conspectus being more general in scope with less specificity, and therefore, not possible to give in depth review of the subject, while a prospectus, being a precursor to a contemplated business venture, should be more detailed to given the prospective investor more/enough information to make an educated decision on the risks of entering into the venture. It still seems odd. The "con" prefix shouldn't diminish the importance of the summary nor the "pro" prefix unduly elevate the summary, yet, these prefixes seem to lead to the conclusion that the "con"spectus should be viewed "with" other information, not alone, but a "pro"spectus would be sufficient "in the place of" any other information which could or should be available prior to entering into a contract. Would a Court view review of a prospectus alone as sufficient due diligence? I hope not! Otherwise, I would hope that the prospectus were not a mere summary as indicated by the definition, but were something more comprehensive, ironically, as stated as the possible first definition for conspectus. So, again, we are left with words which in usage, etymology and just common sense don't appear to work properly to convey the correct unique meanings. Perhaps they have just been used interchangeably improperly for a while that the misplaced contextual meanings have now been added. But I'll posit one last theory before I abandon this conundrum for a better activity at this hour: prospectus was first originated c. 1760, and conspectus c. 1830, making them both relatively new words to English and relating to marked periods in history for socio-economic advancement, therefore, the need for prospectuses and conspectuses evolved, but as technology caught up with the need for specific types of summaries perhaps the definitions have not yet. Thus, while there are myriad and detailed examples of the usage of prospectus, DD has not (and perhaps cannot provide) a single example of conspectus, even from antiquity, or even just under 200 years ago, which makes the actual and continuing use of this word suspect, or at best, antiquated or now at the level of industry jargon. My own cursory Google search showed only a series of journals named "conspectus XXX", which seemed to indicate that it was a compendium of knowledge on a subject (mostly technology, but some business and a fair representation of scientific methodologies). So, for the moment, I'll stick with prospectus, and I'll take all the back up documentation too, thank you!

The email prospectus was too vague for her to feel comfortable with the investment opportunity, although the alleged Nigerian Conspectus indicated that investing in domestic "pyramid schemes" was generally safe.