Recently, I wrote an article titled The Myth of Socially Responsible Investing. The thrust of it was that in a society governed largely by moral relativism (where right and wrong depend on circumstance), the concept of investing responsibly in an absolute sense has no meaning. My reason was that when lines are drawn based on how good or bad something is on a relative basis, those lines are by definition drawn arbitrarily.

A lot of readers got upset with me, claiming my logic implied that if an investor can't be a purist in terms of right and wrong when investing, then he or she shouldn't bother trying to invest responsibly -- or, better yet, in an activist sense -- at all. In truth, that isn't what I meant, and I'll back it up with an example from my own investing shortly. I just asked how one could confidently draw a moral line if the location of that line is arbitrary, and with our complex society presenting a befuddling dimension of interconnectedness: An investor eschewing De Beers, a subsidiary of Anglo-American PLC (NASDAQ:AAUK), for its alleged diamond trade atrocities might be unwittingly thwarting his cause by investing in the manufacturing sector, a heavy user of diamonds. But what if a company is only a moderate user of diamonds? Or buys refined goods made by diamond users? Where do you draw the line?

A way it can work?
Now some of this may be splitting hairs to a lot of folks, but for philosophical types like me, the idea of making inconsistent stabs at an arbitrary target is hard to reconcile. But I got to wondering about ways in which socially responsible investing might be considered logically valid. This is admittedly getting into the domain of logic theory aficionados. But swapping the theory of moral relativism for moral absolutism -- which makes a very definite distinction between right and wrong: absolutes, which, in the theory, never depend on circumstances -- might make things jive with the textbooks. At first glance, an investor "practicing" moral absolutism might be akin to the strong-and-silent-type movie hero of investing: someone less likely to quibble than most, but one who acts decisively once a certain line is crossed.

Proponents of this theory might ask: Would you invest in just anything? Aren't there specific things you would not invest in because they are just plain wrong? Would you invest in things that might be doing some harm to your neighbor or society or our ability to fight terrorism? Do you believe that where you put your money is also a personal statement about your morals, and how you believe corporations should behave? If you spend time doing research on a potential investment, isn't it worth a few extra moments to see if this company is involved in something that makes you uneasy? This is what investing under moral absolutism is about.

An absolute example
While I'm frankly a bit skeptical about the philosophical consistency of moral absolutism, I find myself practicing it anyway. I'll give you an example of something that I consider to be so irresponsible that not only do I refuse to invest in the culpable companies, I refuse to use their products. I'm talking about three large banking chains: Wells Fargo (NYSE:WFC), Bank of America (NYSE:BAC), and U.S. Bancorp (NYSE:USB), and how they abet a government-acknowledged terrorist threat.

The relatively unsecured Mexican border allows just about anyone to enter the country. I'm not here to take a stance on illegal immigration in a general sense. What I am here to discuss is how banks see revenue opportunities in illegal aliens and provide services to them without acknowledging a contemporaneous terrorist threat.

Here's the deal. Over two years ago, Wells Fargo began accepting the Matricula Consular card as valid identification with which to open a bank account. What is the Matricula Consular card? Check this out, but the quick answer is that these cards are issued by Mexican consulates in the U.S. to those Mexicans already here. The only thing someone needs to get one is a birth certificate. Think that's a secure method of identifying illegal aliens? The FBI thinks it's a huge security risk.

I believe Wells Fargo, along with Bank of America and U.S. Bank, a part of U.S. Bancorp, chooses to accept the Matricula Consular card out of greed. By offering accounts to illegal aliens, they can charge them bank fees, commissions, and currency exchange fees on the $8 billion that is wired out of the U.S. to Mexico annually.

Here's the problem. I don't think these banks give a hoot about the security risk the cards represent. How easy would it be for a terrorist to obtain a Matricula Consular card, use it to obtain a driver's license, and from there, a bank account? Then money starts to flow into the account from terrorist sources. Why are we making it so easy for them? The 9/11 hijackers had 63 driver's licenses among them! Where's the outrage?

The moral imperative
Returning to the logic stuff, the logic I offered on moral absolutism has at least one flaw, in addition to the obvious challenge of drawing the line in the first place: By definition, human beings are not perfect. Therefore, somewhere along the supply chain of any company, somebody will behave immorally, and, at least theoretically, void the absolute moral righteousness of the investment. Sure, it's nit-picking to a mildly insane degree, but officially, investors are still drawing a somewhat imprecise line that condones a degree of inevitable impurity.

And there are still a few side issues, such as: Where on the scale do we put companies that are doing really great things for society? And can we offset good with bad?

By now, if your head isn't spinning, I think one conclusion is clear: To this author, there really is no such thing as socially responsible investing in an absolute sense, no matter how it's defined. One can always throw up some kind of counterargument to the "responsible" word. Too many fruits of too many poisonous trees make the notion of absolute responsibility a tough one to prove. I'll offer that a more accurate term is activist shareholder investing.

But despite my penchant for all this semantics stuff, I actually don't think it's something that should keep you from actually seeking to avoid immoral companies. For the offending banks in my example, it could mean voting with your wallets and your investing choices. I feel that businesses need to know if we do not approve of their profiting while whistling past the graveyard -- in this case, one that could hold the bodies of future terror victims.

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Responsible dad and Fool contributor Lawrence Meyers feels it's the cash flow statement that matters most. This article solely represents the opinion of its author and is not a recommendation to buy or sell any stock. The Motley Fool is investors writing for investors.