Well, the actions of corporations are so much more complex than the actions of individuals and are almost never based on a pure, or moral, motive. Corporations, in almost every situation, are based around profit (they are not ALL based around profit, as some are charity organizations.) Corporations don't exist to do what is "right," they don't exist to fulfill their moral duty. Human life, on the other hand, is centered around becoming MORE human, and we exist to find a deeper humanity. We do this by doing what is right, without question. Humans can be held to moral standards because we exist to become more moral, more human. Corporations exist for a different purpose than to be moral and/or more human, therefore their actions can't be held to those same moral standards that dictate the actions of individuals.First, I'm not sure that the greater complexity of corporations is a knock-down argument for their moral "differentness." Think about how complex a human being is, how complicated the decisions we make every day, all the obligations we place upon ourselves, or have placed upon us--legal, moral, familial, societal, to name a few--and you start to realize that, in euan's words, humans "are never and can never be pure." Does this mean their actions can't be moral? I think not. A moral standard is a goal for action, and a failure to reach a goal doesn't necessarily invalidate the goal. (The confusion between what humans--or corporations--do and ought to do is common in these arguments.)
Hm . . . Humans strive to be more human. Corporations strive to make a profit. A corporation cannot take an action because the members of the corporation decide that the action is "right." The actions of corporations always take into account their shareholders, profit, budget, etc.. They are never and can never be pure. Therefore, the actions of a corporation can't be moral, so they ought not to be held to the same moral standard as the actions of individuals. Or something.
Also, does Kant's morality derive from a notion of "purpose?" That claim requires justification. It seems to me to come more from a notion of "good will," which is good in and of itself, the will of an autonomous agent.
Kantian morality might apply to corporations thusly: they should act in a way that they can universally will for every other corporation to act. However, if it can be shown that corporations are not autonomous agents, but are rather inherently "heteronomous," then the Categorical Imperative doesn't apply, and their actions should be held to a different standard.