In his essay “On Worshipping the Right God” (available in his collection God and the Soul), Catholic philosopher Peter Geach argues that:
[W]e dare not be complacent about confused and erroneous thinking about God, in ourselves or in others. If anybody’s thoughts about God are sufficiently confused and erroneous, then he will fail to be thinking about the true and living God at all; and just because God alone can draw the line, none of us is in a position to say that a given error is not serious enough to be harmful. (p. 112)
How harmful? Well, if a worshipper is not even thinking about the true God, then he is not really worshipping the true God, but something else. That’s pretty serious. (I would add to Geach’s concern the consideration that atheistic objections to erroneous conceptions of God can lead people falsely to conclude that the notion of God as such is suspect. That’s pretty serious too.)
Geach takes the word “God” to function as a descriptive term rather than a proper name. It is in Geach’s view more like “the President of the United States” than it is like “Barack Obama.” It’s not clear how important this claim is to his argument, however, given that a key illustration in the essay involves a voter who is confused about who Harold Macmillan is, and “Harold Macmillan” is proper name. The example is dated, but we can restate Geach’s point using a more up-to-date one. Consider someone who says he supports Hillary Clinton for the next presidential election, on the grounds that she is (so he thinks) a staunch opponent of feminism, abortion, and “same-sex marriage.” His reason for thinking this is that the title of her book It Takes a Village and Other Lessons Children Teach Us, which he has not read, is (he supposes) evidence that she advocates small town, conservative family values. Suppose that while he correctly describes Hillary Clinton as the husband of Bill Clinton and the recent Secretary of State, he otherwise has only other hopelessly confused beliefs about her -- that her being Obama’s Secretary of State involved her getting him coffee and taking dictation, that she had once enthusiastically pledged to “stand by my man, like Tammy Wynette,” etc.
Geach would say that such a person does not really support Hillary Clinton at all, but rather some other person who exists only in his mind. Similarly, Geach says, a man who says he is in love with a certain woman, with whom he has only the slightest acquaintance and about whom he has all sorts of grave misconceptions, is not really in love with her but only with some fantasy woman. By the same token, where the conceptions of God associated with two forms of worship are “extremely different,” then “it ought logically to be… a matter of doubt whether both forms of worship canlay hold of the true God” (p. 112, emphasis in the original).
This is so in Geach’s view even if false beliefs about God are associated with important true beliefs:
[E]ven if a natural theologian correctly concludes to the existence of a God with attributes ABC, and those attributes do in fact belong solely to the one true God, we cannot be sure that in worshipping the God whose existence he has concluded to he is worshipping the true God. For along with these attributes ABC the natural theologian may ascribe to his God others which are not those of the true God. Thus, he may like Spinoza falsely believe that God produces all possible creatures, by a natural necessity of fully manifesting his infinite power; or, like many moderns, he may falsely believe that God needed to create a universe full of creatures in order that they, however inferior to him, might be there to love and be loved by -- much as a lonely old woman crowds her house with cats. Was Spinoza, and are these moderns, worshipping the true God, or rather worshipping some vain phantasm…?(p. 114)
But how many errors, and which ones, suffice to lead such a worshipper away from the true God? Geach doesn’t claim to know, but thinks we needn’t settle that question in order to see that the problem is a serious one. About the question of whether Spinoza or the modern theologian Geach describes really worships the true God, Geach writes:
It is not for us to answer such questions; enough to notice that they arise; and there is no reason to doubt that sometimes a natural theologian’s errors may mean that he does not lay hold of the true God in his mind and heart at all. (p. 114)
Catholic practice surely supports Geach’s position. A vivid example is provided by the 2001 decision of the Congregation for the Doctrine of the Faith to regard Mormon baptisms as invalid. Though doctrinal errors are not usually sufficient to invalidate baptisms performed by non-Catholics, and though Mormon baptisms involve the use of what on the surface seems to be a Trinitarian formula, the CDF decided that the Mormon conception of God is so radically different from the Catholic one that the words do not in this case truly invoke the Trinity at all. (Notice that this is the case even though the Mormon language is derived from the New Testament. It thus seems that as far as the Church is concerned, the problem cannot be solved by opting, in the theory of reference, for a causal account over a descriptivist account.)
The Church has also made binding certain views about God’s existence and attributes, sometimes to the point of anathematizing dissent. That certainly shows that the Church regards errors about these matters as extremely dangerous.
The relevance to the dispute between classical theism on the one hand, and the various forms of “theistic personalism” or “neo-theism” on the other (process theology, open theism, etc.), is obvious. In particular, from a Catholic point of view it cannot be emphasized too strongly that the propositions that God is simple, immutable, eternal, and knows even the future free actions of his rational creatures, are all de fide teachings of the Church. These are, of course, attributes that “theistic personalists” or “neo-theists” have either denied or seriously modified.
I am not saying, and I don’t think that either Geach or the Church would say, that no one plausibly labeled a “theistic personalist” or “neo-theist” is really worshipping the true God. The reasons are that some degree of error is consistent with worship of the true God, and there is some flexibility in notions like simplicity, eternity, etc. But there are limits to the degree of error that is consistent with true worship, even if it can in some cases be difficult in practice to know when those limits have been reached.
The point is that, as Geach says, “we dare not be complacent” about the question. It matterswhether a man loves a real woman or only a fantasy, and whether he votes for a real candidate or only one he has constructed in his mind -- even if it is difficult to know in some cases whether the object of his love or his political support is real or imaginary. How much more does it matter, to true worship and to sound apologetics, whether one’s conception of God is correct?