There's always going to be a little bit of autobiographical content to everything. It's how you lend some authority to what you write - you give it that weight by drawing on your direct experiences and indirect experiences from people that you know well, or a little.
As a songwriter, you tend to develop your own style, your own technique, based around what it is you're trying to write and perform, in terms of your own music. So a way of evolving a guitar style as a songwriter is much easier, I think, than developing a true style of your own just from listening to music or playing other people's music.
In writing lyrics - well, for me, anyway - it's about getting into character, you know? 'Who is writing this?' In the case of the original 'Thick As A Brick,' supposedly a precocious, very young child who's fantasizing about his future and the context of all the confusing elements to which school boys are subjected at that time.
