Suppose you have a good reason R1 to do X. Then along comes a second good reason R2 to do X. Does R2 remove the justificatory force of R1? Obviously not. Does R2 leave the justificatory force of R1 unchanged? No again. Clearly, R2 augments the force of R1. Any additional good reasons R3, R4, ... Rn, would of course only add to the justification for doing X. What we have here is a cumulative case for doing X, a case in which the justificatory force of the good reasons is additive.
A thorough discussion would have to distinguish between cumulative case arguments in which each reason is sufficient to justify the action envisaged, and cumulative case arguments in which one or more or all of the reasons are individually insufficient to justify the action envisaged.
Suppose each reason in a cumulative case argument is individually sufficient to justify the action envisaged. Then in what sense are the reasons additive? They are additive in that each additional sufficient reason provides an additional fail-safe mechanism. If an agent has many reasons each of which is both good and sufficient for doing X, then, if one of the reasons should turn out to be either bad or insufficient, then the other reasons are available to shoulder the justificatory burden.
Apply this to the Iraq war. One reason for going to war was the widely shared belief that Saddam had WMDs. Another was that he was a known sponsor of Palestinian Arab terrorists and a reasonably surmised sponsor of other terrorists. (On the second point, see Stephen F. Hayes, The Connection: How al-Qaeda's Collaboration with Saddam Hussein Has Endangered America, Harper Collins, 2004) A third was humanitarian: the liberation of the Iraqi people from a brutal dictator and his sons. A fourth was to enforce unanimous U.N. resolutions that this august body did not have the cojones to enforce itself. A fifth was to end the ongoing hostilities, e.g., Iraqi attacks on coalition warplanes. Even if no one of these reasons is sufficient to justify the invasion, the five taken together arguably provide good and sufficient reason for the action.
The strategy of ‘Divide and Conquer’ cannot be used against a cumulative case argument. Suppose Jack has several reasons for marrying Jill: she’s nubile and pretty, moneyed and witty; they are physically and psychologically compatible; they share the same values; she has beautiful eyes, and there is beauty at the opposite pole of her being as well. So Jack has nine good reasons. It simply won’t do to point out that each of them, taken singly, is insufficient to justify the marriage. A good reason is not the same as a sufficient reason. A good reason can be either sufficient or insufficient. What then are examples of bad reasons? A bad reason would be her having a police record, or her having a doctorate in biology when her doctorate is in mathematics.
The point is that several good, but individually insufficient, reasons can add up to a good and sufficient reason. If so, then ‘Divide and Conquer’ is a fallacious form of refutation. But that is what many leftists do when they oppose the Iraq war. Suppose that the cumulative case consists of R1, R2, and R3, each of which is insufficient by itself to justify doing X. The ‘Divide and Conquer’ objector wrongly infers ‘no reason’ from ‘insufficient reason.’ Thus he thinks that if R1 is insufficient, then R1 is no reason, and similarly for R2 and R3. He then concludes: no reason + no reason + no reason = no reason. He fails to appreciate the additivity of individually insufficient but good reasons, just as the typical poor person fails to appreciate the additivity of the small amounts of money he throws away on cigarettes, lottery tickets, and overpriced convenience store items.
For example, if a conservative gives liberation of the Iraqi people as a reason for the invasion, the leftie is likely to object: "But then why don’t we liberate the North Koreans?" This is an asinine response since it it is based on a failure to appreciate that the liberation reason is only one part of a cumulative case, not to mention the fact that an attempted liberation of the North Koreans could easily lead to nuclear war. Granting that liberating the Iraqi people is an insufficient reason for the war, it does not follow that it is no reason at all. It is a good reason which, though insufficient taken by itself, is part of a cumulative case which amounts to a good and sufficient reason for the war.
Another mistake that leftists make is to confuse a reason with a motive. They do this when they say that a proffered reason is not the real reason. A reason is a motive when it plays a motivating role within the psychic economy of an agent. Suppose Jack has available to him an objectively good reason R for marrying Jill. But Jack is not consciously or subconsciously aware of R. Obviously, R can play no role in the etiology of his envisaged action. Yet R remains an objectively good reason for performing the act in question. A good reason need not be a motivating reason, and a motivating reason need not be a good reason. The expression ‘real reason’ should be avoided because it is ambiguous as between good reason and motivating reason.
Suppose Bush II’s sole motive for invading Iraq was to avenge Saddam’s assasination attempt on his father, Bush I. Even on this wildly counterfactual assumption, there were good reasons for the invasion. For an action to be justified, all that is required is that there be objectively good reasons for the action; it is not necessary that the agent’s motives be objectively good reasons. Even if an agent is not justified in doing X – because he is either not aware of or motivated by the good reasons for doing X – the act itself (the act-type itself) can have justification. Our man Jack, for example, may be driven to marry Jill by his lust and nothing besides; but this does not entail that his marrying her lacks justification. Jack’s father might say to him: "Son, you made the right decision, but for the wrong reason." The rightness of the decision is due to the availability of good reasons even if horny Jack did not avail himself of them.
At this point an objector might maintain that what I am calling good reasons are simply ex post facto rationalizations.But a rationalization after the fact is not the same as a good reason that plays no motivating role in bringing about the fact. For a rationalization is a bad reason. Suppose Ali physically assaults Benjamin because B is a Jew and A believes that Jews are the "sons of pigs and monkeys." After the fact, A explains his behavior by saying that B insulted him. Suppose B did insult A. A is rationalizing after the fact as opposed to giving a good reason after the fact. B’s insulting of A did not give A a good reason for initiating physical violence against B.
Now let us suppose that Bush II’s sole motive for ordering the Iraq invasion was his desire to deprive Saddam of the WMDs that he, Bush, believed Saddam to possess. Suppose, plausibly, that the belief is false. In that case, Bush II’s motivating reason was not an objectively good reason – based as it was on a false belief – but it could still count as a subjectively good reason in this sense: he had a reason that was a good reason based on the information he had available to him at the time of the decision. I would then argue that the other reasons, which are objectively good, bear the justificatory burden.
An astonishing number of people, some of them intelligent, believe that the motivating reason for the Iraq invasion was the desire to secure access to Iraqi oil. But if that was the motivating reason, it is was a very bad reason since (i) the oil was flowing; (ii) starting a war with an opponent believed to have WMDs and known to have ignited oil wells in the past is clearly a stupid way to secure access to Iraqi oil; (iii) the projected cost of the war would be scarcely offset by the value of the oil secured; and (iv) deposing Saddam and his sons was not at all necessary to insure the flow of oil. I would argue that since this oil reason is so obviously bad, it is not reasonable to impute it to Bush and his advisers as the motivating reason for the invasion.
To sum up. The case for invading Iraq was a cumulative case. A cumulative case cannot be refuted by ‘Divide and Conquer.’ A good reason need not be a sufficient reason. A reason is not the same as a motive: there can be objectively good reasons for an action even if the agent of the action is not motivated by any of these reasons. To find good reasons after the fact is not to engage in ex post facto rationalization. This is because a rationalization is the providing of a bad reason.
But of course, liberals and leftists are so blinded by their passionate hatred of Bush II, that patient analysis of the foregoing sort will be lost on them.