What is conscience and when should we follow it?

I plan to post some unpublished material that’s been accumulating over the years, over at my main website.  First up is a lecture on the theme “What is Conscience and When Should We Follow It?” which I’ve given a couple of times but has never seen print.  Is conscience a kind of emotion?  A kind of perceptual faculty or “moral sense”?  An operation of the intellect?  Or some sui generis faculty?  When are we obligated to follow conscience?  What is a lax conscience?  A scrupulous conscience?  A doubtful conscience?  What does the Catholic Church teach about these matters?  These issues and related ones are addressed in the talk.