Gal 1:13-17; 2:11-21
It's when you try and explain something that you get all tied in knots especially about God. There is nothing like a good story: far better for shaping what we believe than Paul trying to explain stuff with all that language about justification and law. I know that is probably heresy to some who love a good debate but when Paul writes we don't really know how he understands these words nor do we have the original letter he is answering and he is writing to specific congregations rather than the whole global church which, if he was, I rather think he'd say things differently.
One commentary on a site called 'Working Preacher' suggests changing every 'justification' to 'belong'. This is a good thing especially for us here where we talk far of belonging first then believing. If we baptise infants, which we did just yesterday, then 'belonging' makes much more sense and is more honest about what we are doing than expecting a baby a few months old to believe.
Belonging is about having a place called home, a place where others know you, love you, support you and gather with you. Believing doesn't have any of that sense at all but is quite individualistic. Anyway, before I go off on a hobby horse rant, go read the passage with belonging rather than justification and see what it does to the sense...