Mr Fool said-
Is it a fair analyze that a "soft atheist" is not sure, but just suspect that God MAY not exists (like 55/45 % in chance)
and a "hard core atheist" is convinced 100% (he "knows") that God does not exists? (100/0 % in chance)
The distinction is not really about a numerical estimation of certainty (for statisticians, the confidence interval of one's being correct, the certainty), as much as the claim one wishes to make AND the strength of the supporting evidence they have to prove their assertion to others.
Remember, the idea of proof is very different when used in the legal arena vs that used in the world of mathematics, with its absolute 'perfect' proofs. The courts use different standards, based on the seriousness of the charges, eg "beyond a reasonable doubt", "the preponderance of the evidence", etc. Few bother getting into the legal standards, other than it's good to realize that waiting for ABSOLUTE proof or certainty defore deciding on ANYTHING is silly.
If I assert, "no God exists" (hard atheist), then the burden falls on me to prove the claim.
If someone asserts, "Gods exists" (theist), then the burden falls on them to prove the claim.
If I don't hold or accept any beliefs in Gods, it's because I have no rational grounds to support the belief: I'm a "soft atheist". I have no burden to prove anything to anyone, since I'm not making any claim on God's existence, either way.
In contrast, both the theist and hard atheist have to support THEIR claims by producing evidence.
There's overlap between the agnostic and the soft atheist, such that they're synonyms. I'd just as soon disgard the term agnostic, since the term 'gnostic' involves the old-fashioned concept of God-given knowledge.
Adam