I imagine I make both types of arguments from time to time and issue to issue.

I did find it interesting to compare the two types of argument to the writing done in a discipline I'm fairly well acquanted with, history.

Broadly speaking, a great deal of historical literature deals with motivation, which is often tightly integrated with intention. Why did so-and-so do such-and-such? As you point out, even given intimate and detailed writings by the person in question, it's still impossible to know someone's mind. People exagerate and lie, they leave memoirs that are intended to soften the glare of history's illumination rather than sharpen it.

I think a similar analysis of current events is not without value. Motivation is important, and the surface often does mask what lies below. We may never know with any certainty, for instance, why Saddam behaved the way he did in the lead-up to the invasion, but the desire to speculate is not only a part of human nature, imho, but informed speculation might lead us to consider possibilities that we'd otherwise miss.

A type M argument would be to write, as you did on September 9, that, "It's now clear that the Iraq war was the mother of all bait-and-switch operations. Mr. Bush and his officials portrayed the invasion of Iraq as an urgent response to an imminent threat, and used war fever to win the midterm election." This is not a constructive argument. My opinion is that it requires an implausible degree of complicity among highly dedicated civil servants.

http://www.techcentralstation.com/100703B.html

Note that his disagreement is with the argument itself, not the manner of argument. Further, the terms of his disagreement are--as he states--opinion. Which is all well and good. The discussion as laid out lacks evidence on both sides, but I don't see anything wrong with it as a starting point. It's important for us to understand why we went to war, and also to realize that we may need to dig hard to get nearer to the truth.

Furthermore, I still care far more about consequences than about motives. If the consequences of the Iraq war are that it leads to increased terrorism and conflict, then even the purest motives would not make it a good war, and vice-versa.

Agreed, but I think he's missing the flip-side: if the motive behind the war in Iraq was empire, then even a decrease in terrorism and conflict wouldn't make it a "good war." (Assuming we can all come to the agreement that overseas empires are just not on anymore...also, just so we're looking at the same page, I personally don't think the US is planning to gather a bunch of colonies under the stars and stripes.) So motives are important...they are a compliment, in a way, to consequences. The latter may have a more immediate and keenly felt effect, but the former can have a very real impact as well.

It's kind of like the difference between strategic and tactical, with motive taking the higher role. It's from that level that patterns and trends can emerge.

Another interesting point: Saddam's motives and intentions, neither of which we knew with certainty before the war, were apparently still of sufficient importance to carry the invasion. Yet now, motivations and intentions are somehow not a reasonable basis for discussion?

Curious...