Echoing what Marxist said - I read through the excerpt and felt fairly certain that Leahy was going to be a professor of Philosophy focusing in the analytic tradition. It's dense work to be sure, but I'd agree that rather than bad writing it actually is just a) in-depth and b) written like philosophical works tend to be. This took me back to trying to muck through Kant's Critique of Pure Reason. Blech.
You do need some academic background in philosophy to get through readings like this, and even "easier" excerpts like you might read in Aristotle's Metaphysics, Plato Republic, or Descartes' Meditations (not saying they're easier to be pretentious, but because they are often the go-to works for introductory philosophy courses) are written and translated - essentially, presented - using language in a way that is completely different from how we're accustomed to reading works in other academic pursuits (including any other humanities, social sciences, fine arts).
That being said, while I was in school I found the best way for me to try to get through texts like the one you shared here, whymeo, or the ones I mentioned (or the authors Marxist mentioned!) is by reading them aloud. It forces you to slow down a bit and figure out where the emphasis is supposed to be and how the sentences are actually supposed to be understood. Some of the work I found most valuable and challenging, especially in my freshman year, was writing summaries of excerpts in my own words.
Thanks for sharing, I'm kind of interested to read this (I probably won't end up doing it, but maybe I'll find a summation online). :) Also, everyone should consider taking an intro to philosophy course if you get the opportunity. Bit off topic but the widely accepted view of philosophy in popular culture is grossly misinformed and based loosely on those pesky continental quacks who ruined it for the serious guys! (No offense to those of you who are into continental philosophy!)