Now, to study the technical definition of "Khawarij" from the perspective of some Shia scholars (who I will admit, I am generally less familiar with). Sheikh Muhammad Abduh [Nahju Al-Balagha Vol. 1, pg 78] attempts to explain the concept of what the Khawarij are more clearly than Sunni scholars by saying "the Mariqun [Khawarij] are those who have gone out of the religion, who have doubt and who are not sure, and he [Ali] crushed them with arguments and defeated them!"
To go out from the religion I personally would have to consider a Muslim to a. either commit extreme shirk of worshipping something other than Allah, b. to disregard the sunnah of the Prophet Mohamed sallalahu alahi wa salaam as being part of the religion, c. to give up prayer, ect. We know from history, that this is not so of the people of Nahrawaan. And if you are Shia, you will know this because Ali himself said they were not infidels/disbelievers.
To have doubt, to me personally, means, that the people of Nahrawaan's belief in Allah and the hereafter was weak. This is not evidenced at all, and is contradicted entirely for any Shia scholar who would state it is so by Ali's own statement about the people of Nahrawaan: "From infidelity they have already fled; and a hypocrite seldom remembers Allah." [Al-Baihaqi Al-Kubra Vol. p. 334, narrative no. 17189]. Meaning, Ali himself in history acknowledged that the people of Nahrawaan remembered Allah frequently. In fact, the people of Nahrawaan are always mentioned as praying constantly, especially by Sahaba companion Ibn Abbas, and Ali.
As for whether or not Ali crushed them with arguments and defeated them, he did indeed defeat them in the skirmish battle at Nahrawaan. But with force, not arguments. To clarify this, from Ali himself : "They are the people who have rebelled against us, and we have been given victory over them." None of Ali's arguments changed the so-called Khawarijites opinion, for indeed, Ali himself had been of the same opinion as them originally about Muawiya's tactic of raising the Qu'ran copies on spearheads saying "what is between these pages is the judgement between you and us" to keep the war away from them awhile while they were at the disadvantage to Ali's forces. Short history lesson: Ali's side had ALREADY tried negotiating with Muawiya's side on NUMEROUS occasions. Ali was no fool and realized a pause in the fighting right now was advantageous to Muawiya. Originally, like the people of Nahrawaan, he did not wish to agree to this truce, but the majority of his fighters did so he changed his position. Historically sahih (from a Sunni perspective) ahadith also corroborate from Muawiyia's advisor Amru bin Al Alas himself that this was not a sincere act of truce, but a military tactic. "Let us raise copies of the Qu'ran on spearheads as a sign of wishing to end this war… so that we may stop Ali's forces and weaken their strength." [Al Yaaqubi Taarikh Al Yaaqubi, Vol. 2, p 188].
Ali would have been in no position to persuade the so-called Khawarijites with arguments, seeing as he had originally stood adamantly with them. In fact, the people of Nahrawaan's arguments were so compelling that companion Ibn Abaas was persuaded by them. It is my personal belief after reading all accounts from Sunni and Shia sources of the incident, that Ali would have preferred to stand on the same side of the fence as the people of Nahrawaan, who rejected the pseudo truce agreement shouting "There is no judgement except that of Allah." Except that it was NOT the wish of majority whom he led, and since it led to disunity he was quoted saying "That is the word of truth behind which wrong is intended." [Al Tabari Al Taarikh Vol. 6, p. 17 (and numerous others sources saying the same, both sunni and shia)].
If you believe that Ali was sinless like Mohamed salalahu alahi wa salaam (I do not), you would have to believe that by saying that Ali meant that the people of Nahrawaan were right, but that there was more to be considered than that alone. Or, authoobillahi minash shaytaani rajeem, astighfuraAllah, that Ali received Divine revelation from Allah (I totally DOOOOOOOOOO NOT and believe to believe so IS shirk). If you think it is meant literally, than this would be a mistake of Ali's as no man is allowed to judge or assume intention. I say this with authority because of the case that a disbeliever proclaimed "la ilaha il Allah" and a Sahabi slew him. When asked by Mohamed salalalhu alahi wa salaam why he did so, the Sahabi said, "He did not do so except in fear of the sword." The Prophet angrily asked him: "Have you split his heart to see what exists therein?" So without Divine revelation, no man can pass judgement on another man's intention.
We know that the action of the people of Nahrawaan were honest, and even Ali says it was the truth. They rejected the false truce under the same pretexts that Ali had given for the war having been justified in the beginning. Perhaps, later having reconsidered what he knew about judging intentions to be for Messengers and Allah alone, Ali came to rule his followers about the "khawarij": "Do not kill the Khawarij after me, for he who seeks the truth but mistakes is unlike he who seeks misguidance intentionally [Muawiyia and his Syrian forces]. Scholars will say that Ali speaks of Muawiyia as one who seeks misguidance intentionally, and the Khawarij as those who do so accidently, but I feel more Ali was speaking about his own followers, when they chose to make the truce in error. BTW, the last statement is biased so feel free to strike through if you like. This is me trying to give Ali an out for a mistake I believe history would have him make.
At least from Ali's opinion, and thus I must conclude what should be the Shia one regardless of what their scholars say, the Khawarij didn't leave Islam like they regard Muawiyia to have done. They still regard them as Muslims, but as Muslims who will not follow majority opinion if it contradicts what they know of Qu'ran.
I have not found a single Sunni source that can tie in the "what is Khawarij" with "who" the Khawarij are purported to be alas. Abu Dawood says of the people of Nahrawaan "They are no people who follow their prejudices… they are the people whose traditions are the most authentic" and even Ibn Taymiyya says: "they are well known to speaking the truth to the extent that the traditions narrated by them are the most authentic of all" [Minhaj Al Sunnah Vol. 3, pg. 3]. So much so for the old "they innovated" argument, then I guess.
SUNNI: So the Sunni technical description of "Khawarij" is people who are adamant followers of the Prophet Mohamed's traditions and honest to the point of being highly quoted by all ahadith scholars, yet they [people of Nahrawaan] left Islam and created the first disunity (which they didn't) somehow by disregarding Ali's military decision which cannot be evidenced from any of their decisions/actions concerning creed and tauhid, especially when reading from the perspective of respected companion and sahabi Ibn Abaas.
BTW, I follow Ibn Abaas over a lot of Sunni Scholars. For instance, he said the eye rims [aka kohl applied in the rim of the eye, makeup of the time upon the Salaf] was halal and what is apparent of. Yet I've never read Saudi Sheikh Ibn Baaz say the same right? Ibn Abaas walked with Rasoolulah. I'm going to take his word first, unless the hadith is proven to be fabricated or inaccurate ect.
???? (This is KIND OF why I don't follow scholars blindly when I can have daleel [Islamic evidence] instead).
SHIA: The Khawarij are those who rebelled against Ali's majority forces' decision to accept Muawiyia's fake truce. They were neither the first callers of disunity, nor did they leave Islam, but their actions are regarded as an innocent but misinformed mistake. [This is me taking Imam Ali over Shia scholars because he's more authorative I'd figure].
OOOOOR Ali himself admits his forces majority were mistaken, as I concluded [not a shia though so my opinion here doesn't count].
IBADHI: The people of Nahrawaan did not go out of Islam, but defended it to the letter even from their friends and allies. If the definition of Khawarij is one who rebels against a right leader, the people of Nahrawaan believe a leader must always lead by Qu'ran and Shariah and within its pretexts, and not simply be a leader regardless of Shariah legality. If right leader means someone injust, who disregards Qu'ran and sunnah, then this is not Islam they have gone out from, but from tyranny and corruption.
(K, I am not Ibadhi, and I don't know yet about LATER Nahrawaanese practices of Islam, but I agree about RIGHT LEADER).
So technical definitions now all dealt with in the highly confusing mess that they are, we will now delve into how the term "Khawarij" has been used historically.
What are YOUR thoughts on this thus far? Any takers?