Well, since no one has responded yet, I'll try to help you out a little. I just want to make it clear that I have a pretty limited understanding of music theory, and I'm not a huge fan of it anyways... its great when it makes sense to you, but it often degenerates into huge, technical discussions that really have nothing to do with playing the guitar better... so with that said, here goes:

Originally Posted by: WhuneThis is probably incredibly elementary;
but I think I've just had an aha moment:

a half-step is a minor 2nd
a whole-step is Major 2nd
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I think you're going to get confused quickly if you start looking at & describing scales counting in this way. From what I understand, you normally keep counting from the "tonic" or root note of the scale. So your major scale is Unison, Maj 2nd, Maj 3rd, Perfect 4th, Perfect 5th, Maj 6th, Maj 7th.

There's nothing wrong with thinking in terms of "whole steps" or "half steps" (or "tone" & "semi-tones" if you prefer), especially if it avoids confusion.
[QUOTE=Whune]
by the way: why is it called a "perfect" Fifth?

I believe its called a "perfect 5th" when it spans 7 semi-tones, as opposed to augmented or diminished that would add/subtract a semi-tone respectively.

I would STRONGLY recommend that you pick up this text book:

http://www.amazon.com/Guitar-Fretboard-Workbook-Understanding-ebook/dp/B002G1ZHNQ/ref=sr_1_1?ie=UTF8&qid=1358137920&sr=8-1&keywords=guitar+fretboard+workbook

Its super cheap, and will really help clarify the theory basics for you... not just in your head but also visually on your guitar as well. I've recommended it to other members who have really liked it. Its by far the best book on theory for guitarists I have ever come across. Hope this helps!