On Shabbos I had the opportunity to further look into the definition of apikorus, following the trail of the Chazon Ish I quoted earlier.
First, contrary to what SoRight writes, it is 100% impossible that the Chazon Ish would ever had said that a frum Jew who keeps Torah and Mitzvos is an apikorus, since, as I mentioned ear;lier, one needs to be porek ol to fall into that category, and live one’s life in a manner inconsistent with Chazal. This is even according to the strict opinion of the Rashba, I believe, who says one who denies Torah Shbeal Peh is an apikorus. As I posted earlier, the Chazon Ish said from the fact that a Kusi can shecht, it is clear that more than bad hashkafas are needed. What is needed is hefkerus (from which the word apikorus is derived). So if it is a choice about believing some hearsay story, or what the Chazon Ish wrote in his own hand in black and white, I will go with what he wrote.
But let us look at Shitas HaRambam. In Hilchos Shechita (4:14)
????? ???? ?????? ?? ??????? ???? ????? ??? ?? ???? ?????? ????? ????? ??? ????? ?? ????? ???”? ????? ????? ?? ????? ?? ???? ?????? ????? ???? ?????. ??? ??? ???? ?????? ??? ?? ???? ??? ??????? ?? ???????? ???? ????? ????? ????? ????? ??? ??????? ?????? ????? ??? ??? ????”? ??????? ????
An apikorus is one who denies the Torah and Moshe Rabbeinu (and certainly one who denies the RBSH). He is like a gentile and his shechita is neveila.
But in Halacha (4:16) the Rambam writes:
??? ??????? ?????????? ????????? ??? ?????? ?????? ????? ??????? ????? ???? ?? ?????? ?????. ??? ???? ?????? ??? ?? ?????. ???? ????? ?????? ??? ??? ?????? ??? ???? ??????? ????? ?????? ?????
???? ?????? ???? ?? ??????
We see that EVEN ONE WHO DENIES THE ENTIRE TORAH SHEBEAL PEH IS NOT AN APIKORUS, AND HIS SHECHITA IS KOSHER.
So now getting back to the opening post, does anybody seriously think any knowledgeable Rav could have possibly labeled Rav Kook an apikorus? On what grounds? Obviously this is another one of these hearsay stories which have no factual basis.
To sum up, as Jay11691 put it so beautifully in the name of Rav Schwab, just because one disagrees with the Yeshivishe hashkafa does not make one an apikorus. The only thing that does is to totally deny Moshe Rabbeinu, the entire Torah or the existence of the RBSH. Quite possibly there is also an additional requirement that one must actually live a lifestyle of hefkerus, as is mashma from the Chazon Ish, and from the language of the Rambam in Avodas Kochavim (2:5) where he says Ad shenimtzeu ovrim al gufei Torah as below:
??????????? ?? ????? ??? ?????? ??? ?????? ????? ?????? ?? ?????? ?????? ?? ???? ???? ?????? ???? ???? ??? ??? ??????? ???? ??? ???. ????? ???? ???? ?????? ????? ????? ??? ????? ??? ???? ?? ??? ????. ?????? ?? ???????? ?????? ??????:
I rest my case. (Thanks to HebrewBooksdotOrg for the text.)