Originally posted on http://vapourstation.blogware.com/ Mon 12 Jan 2009
The guitar is an instrument you play music on. Theory is a system which serves to label, organise and explain notes, how they fit together and make sounds which are 'popular', how they look on the page when notated, and how they relate to each other with fancy names. A lot of the time these 2 things cross over because when you play notes on the guitar, theory has a name for them. The same is for scales and chords but ultimately, on the guitar they are noises and sounds. Theory is just a system of labelling.
If you want to know how this labelling system relates to the guitar, in contradiction to popular opinion, it doesn't. The guitar is an instrument which you use to create notes (either on their own or in combination) which you either like the sound of, or don't. Theory is a system of labels for these noises.
If you want to learn theory, it’s worth establishing a purpose first. Why? This way it's easier to find what resources you may draw upon to ensure that you learn exactly what it is you want to know, thus avoiding having to trawl through a whole load of theory which you're not actually interested in.