Can I cite an old book in my research proposal without having read it? Here's a small dilemma. I have a few ideas that I am putting into the form of a research proposal. It borrows heavily from the insights of David Ricardo's Theory of Comparative Advantage. Now, the notion of comparative advantage is pretty much common knowledge in economics. However, my proposal is for research in Complex Networks. 

Should I cite David Ricardo's original book from 1817 in which he published the idea, without having read it? (I doubt I'll be able to follow the argument easily in Enlightenment-period English) Or should I cite a secondary paper by someone more modern that talks about and analyzes comparative advantage? I would prefer the latter route as I would actually be able to read the material that I'm citing, but then I will not be going to the source of the original idea.
You need to read the material you cite.  That does not mean you need to read an entire book if the relevant portion is in one or a few chapters, but just plopping in a citation without ever cracking the cover is reference padding and is academic misconduct.

You've been given good advice by J. Fabian Meier about also citing newer material, but you can't cite something you haven't read.