To really know Karate from a practical, principles based approach -
To really know Karate from a practical, principles based approach - you have to go deep with Naihanchi.
Start by studying Choki Motobu's history/biography.
Then just go deep google on Naihanchi. Read about it, watch the videos, etc.
I agree with the hard core karate traditionalists on this - If you want to use Karate for dirty street fighting and keep it practical, you'd have to base your practice on Naihanchi.
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I think the above sentiment ties in with this thread. There's a deep root to all traditional martial arts that's grounded in a couple of core principles which can adapt to many situations. Sometimes that root is so deep that it's hard to find. But, like I said - if you spend enough time in an art, keep an open mind, work hard, etc - you'll find it.