If somebody asked me to define the Rock and Roll Spirit of 1970s (something I just coined, I think), I would use this video as Exhibit A.
Humble Pie playing "I Don't Need No Doctor". The song oozes fucking Rock. Let's start with the title which proudly flaunts its non-grammar in your face. I don't need no doctor? Brilliant. Everybody used the double negative in their songs at this time. And why? Because they fucking could. If nothing else, it sounded better. I mean, take the alternative: "I Do Not Need A Doctor." That sounds like a Sesame Street tune. I Don't Need No Doctor sounds like something a Hell bound trucker clutching the wheel of a runaway 18 wheeler engulfed in flames would say.
Second, the song has no premise and little message. The fact that he "don't need no doctor" just proves he (Steve Marriot, specifically) is a fucking bad ass-- in a Rock kind of way.
Third, the proud opening of "I don't need no fucking doctor", like the infamous "It's time to kick out the jams motherfuckers!" is a brilliant piece of stagemanship, throwing the audience off and kicking it into high gear. Follow it up with some teeth gnashing power chords, a face melting guitar solo, a grooving break-it-down, and a series of false endings, and you've got yourself a Heavy Metal song that had class. None of that black leather, goblins, and cannibal bullshit that came out 10 years later. This has sex. That was shit.
Fourth, consider the history. Steve Mariott was in the Small Faces (which, after Mariott's departure, later became one of my favorite bands, The Faces). The Small Faces recorded such poopers as "Itchycoo Park". Check it out:
Yeah, there's Mariott front and center singing "feed the ducks with a bun" in proper Mod wear, complete with dinky guitars and childish harmonies. Then he grew up, grew out his hair, and learned how to rock. Good on 'em.
So grab your guitar and harmonica, your bottle of Jack, and your best mates, and when they tell you that you need to seek medical help-- you know what to say.