K-man
I am of the school that believes that 'blocks', as such have very little place in the martial arts. We will sometimes move in and jam but to actually block an attack signals the end of your opponent's first technique and the trigger to launch his next attack.
Now, evasion can mean two things. Firstly, we move off the line of attack as in ashi tsabaki. That gets us out of the firing line, especially if someone is charging us. The disadvantage is that our opponent mostly retains control of his centre and can easily redirect his attack. Secondly, as Seasoned pointed out is tai tsabaki where we intercept and redirect the opponent's attack, most often breaking his balance and creating the opportunity to strike or apply any other suitable technique.
The secret to all this is to go back to our basic 'blocks'. In Goju, almost without exception, they are two-handed. The first hand deflects the attack and the second hand is actually a strike. Unfortunately, very few instructors teach this application, prefering instead to teach the obvious application. My question to them is, "Would you ever use the blocks you teach in a bar or street situation?" The answer is inevitably "Well no ... but, ..... !!" The next question becomes, "Then why teach them at all if you wouldn't use them in real life?"
