Someone who has actually tasted truth is not contentious for truth. Someone who is considered by people to be zealous for truth has not yet learnt what truth is really like; once he has truly learnt it, he will cease from zealousness on its behalf. (Kephalaia IV.77; The Wisdom of Saint Isaac the Syrian, translated by Sebastian Brock)
When I first came across this passage of St. Isaac a few months ago, it grabbed my attention forcefully because I recognized its truth in myself (and not because I'm "someone who has actually tasted truth"). As I've listened to the reflections of wiser men than myself, I've began to glimpse its profundity, far greater than I first imagined. In just a few words, this bishop who lived in the seventh century on the other side of the world diagnosed a spiritual sickness that is running rampant to this day.
Before I can begin to explore more of what St. Isaac meant, a bit of ground-clearing is in order. He wrote against being "zealous" or "contentious" for truth, but aren't we supposed to have zeal for God (Rom 10:2, 2 Cor 7:11), and "to contend for the faith that was once for all delivered to the saints" (Jude 1:3 ESV)? How can Isaac proscribe what God commands?
The first thing to note is that as his title implies, St. Isaac the Syrian was not writing in Greek, but in Syriac, so of course the words he used for "zealousness" or "contentious" are not exactly the same ones used in the New Testament. This makes possible the same kind of semantic slippage that we see in the denigration of the "passions" (epithymia) as dangerous and needing to be subdued both in the New Testament (Rom 6:12, Gal 5:24, Tit 2:12) and in the Orthodox tradition, whereas today the word "passion" is used much more positively, especially in Evangelical Christianity, to mean a God-given affinity or calling to something that is generally worth following.
I don't know a word of Syriac, but I can at least investigate how the New Testament speaks of "zeal" or "contending". The word used in Jude 1:3 is unique in the NT, but it is constructed from the more common root agonizomai, "I struggle/fight", used by Paul to refer to "fighting the good fight" (1 Tim 6:12, 2 Tim 4:7), as well as striving in the work of God (Col 1:29) or to lay hold of salvation (Luke 13:24). Paul uses it to metaphorically describe the way of Christ as a foot race in which we compete for the prize, salvation (1 Cor 9:25). Just once is it used negatively, to refer to physically fighting in John 18:36.
The Greek word for "zeal", in both its noun and verb forms, is more mixed. It frequently denotes envy, jealousy, or coveting (Acts 7:9, 13:45 17:5, Rom 13:13, 1 Cor 13:4, 2 Cor 12:20, Gal 5:20, Jas 3:14,16, 4:2) and can also mean indignation (Acts 5:17, Heb 10:27). But it can also be rendered as earnest desire (1 Cor 12:31, 14:1,39) or simply "zeal" (John 2:17, Rom 10:2, 2 Cor 7:7, 11, 9:2, Phil 3:6, Col 4:13, Rev 4:19). Paul writes that "it is good to be zealous in a good thing always" (Gal 4:18 NKJV). Paul is "jealous for you [the Corinthians] with godly jealousy" (2 Cor 11:2), and in the Septuagint God himself teaches that he is a "jealous God" (Exo 20:5, 34:14, Deu 4:24, 5:9, 6:15, Jos 24:19).
What it seems to me is happening with these usages is that zeal/jealousy and contending/fighting/struggling, while literally denoting undesirable qualities, are being used metaphorically to mean something good. I don't know what else to make of "godly jealousy". It's somewhat like how Jesus commands us to hate our parents (Luk 14:26)—obviously he is not commanding us to break the fifth commandment, but calling us to love God so surpassingly above any other attachment that it seems like hatred in comparison.
Most people are already aware of this example; I think something similar is going on with the usage of epagonizomai and zelos/zeloo. Physical altercations and quarrels have no place among God's people, but there is a "good fight" to fight (1 Tim 6:12), and we are to "contend" for the faith (Jude 1:3)—describing how we are to strive for the life and salvation of ourselves and others with the vigor and discipline of an athlete or a soldier. God's concern for the good of his people, that they worship and serve only him, is so strong and stringent that it is described as jealousy (Exo 20:5), as is Paul's (2 Cor 11:2). God wants us to belong to him and not to any idol or lesser thing. When applied to us (Gal 4:18), zeloo probably likewise refers to the fervor, exclusivity, and purity of our devotion to "a good thing", and not anything else. Likewise, the "zeal" for which the Levite Phinehas is commended in Numbers 25:11 (same Greek root) is his concern for the purity of Israel's worship, mirroring God's zeal/jealousy for his people.
Presumably, St. Isaac did not have these positive meanings of "zealous" and "contentious" in mind, but was writing more literally, with the negative connotations not elided through metaphor. I also think he was speaking more with respect to the inner life, whereas the NT authors are metaphorically describing external actions and disciplines by drawing parallels between them and combativeness or jealousy. (This is especially evident in descriptions of God as jealous, which are certainly anthropomorphisms) The Reformed theologian R.C. Sproul paraphrases his peer John Piper as aptly saying "that we not only have to believe the truth, that it’s not enough even to defend the truth, but we must also contend for the truth. That does not mean, however, that we are to be contentious people by nature." I think St. Isaac is highlighting this same distinction, between contending for the truth and becoming contentious.
That wraps up the ground-clearing. The next post will be longer and delve as deeply as I can manage into what St. Isaac did mean.