Philosophers are not necessarily known as great storytellers. But every now and then, a philosophical thought experiment conveys a story that captures the imagination and sinks into the public consciousness. Plato's cave is one of the best examples from ancient philosophy. And in my humble opinion, one of the most enduring modern stories is the Parable of the Invisible Gardener. Originally told by philosopher John Wisdom and then famously retold in an essay by Antony Flew (‘Theology and Falsification’, in Antony Flew and Alasdair MacIntyre (eds) New Essays in Philosophical Theology (London: SCM Press, 1955), 96–9) the basic story goes like this:
Two men walking one day in a jungle came upon a clearing which was overgrown with flowers and weeds. One of the men then declared that the clearing was originally cultivated and is still tended by a gardener. The other man was duly sceptical: as he looked at the overgrown tangle of flowers and weeds, he saw merely another chance clearing in the jungle with no reason at all to believe there was a gardener behind it. And so he challenged his friend that they should sit together and wait to see if the gardener shows up. His friend agreed, confident that the gardener would appear. But after an extended period of time, still no gardener had shown up.
Alas, rather than admit there was no gardener at all, the believer simply tweaked his claim: ‘the gardener’, he now said, ‘is, in fact, invisible’.
Unperturbed, his sceptical friend then suggested that they erect an electrified fence monitored by bloodhounds. That way, they would surely be able to detect the approach of this increasingly elusive gardener. The believer agreed, but the dogs never sniffed anything and there never was a jolt to the fence.
Incredibly, the believer was still undeterred: his next tack was to say that the gardener can walk through fences while remaining undetected by bloodhounds. So perhaps he had been there after all: they just didn't see him.
By this time, the first man had grown understandably exasperated and so in indignation, he threw up his hands and asked, ‘What is the difference, after all, between this infinitely adaptable invisible gardener and no gardener at all?’
As you can probably guess, within this story, the Invisible Gardener represents the theory of theism and the undaunted believer represents the theologian forever modifying his ‘God hypothesis’ to overcome ever new waves of apparently disconfirming data. When this has gone on long enough, you might wonder whether that which is true of an invisible gardener is true of belief in God generally: in short, what's the difference between this invisible, infinitely adaptable god of religious belief and no god at all?
The Parable is pithy and forceful and those qualities have earned it a place in the philosopher's canon of thought-provoking campfire stories. But as with any really good story, it functions best when we use it to further the conversation rather than settle all the questions. And with that in mind, I'd like to take a closer look at the Parable and whether it actually presents a problem for theism. We will do this in two parts: first, we will consider an important part of theory evaluation that the Parable leaves out; and second, we will consider how the precise same story may be told of another very popular theory known as naturalism.
Before we get started, we should underscore the fact that we are here discussing theism as a theory. Within this context, the word theory refers to an explanatory framework for facts, evidence, or data. The Invisible Gardener Theory (henceforth IGT) is a proposal for how to interpret the facts about a clearing in the jungle. It is a viable theory insofar as it provides the most satisfactory overall explanation of all the facts (e.g. the presence of the clearing itself) as well as addressing apparently disconfirming evidence (e.g. the presence of a tangle of weeds and flowers; the lack of appearance of a gardener).
So what is the problem with the IGT and, by implication, theism? According to the Parable, the problem is that the IGT is endlessly adaptable to new disconfirming evidence. But is this actually a good objection? Not really. The Parable fails to recognize that theories generally are, in principle, endlessly adaptable. Consider an automotive analogy: if you discover that your car requires a new transmission, you will need to decide whether it is worth the cost. If you still think the car is useful overall so that it is worth fixing, then you pay for the transmission. The fact is that, fix by fix, you can keep a car on the road in perpetuity, forever addressing problems as they arise. If you are sufficiently committed to a particular vehicle, you could keep it on the road for decades like the Cubans do with their 1950s American cars. But even if you can endlessly fix a car, for practical purposes there may well come a day when the car you now treasure is no longer worth the next mechanic's estimate. At that point, it's off to the scrapyard.
Theories are like that. You can ‘fix’ them endlessly by adjusting the theory here or adding a supplemental hypothesis there. And you can keep doing that just so long as the cost is worth it. And it may be worth it: if you find that a theory has some significant virtues in explaining aspects of reality you may keep it on the road for a good long while. But at some point, you may find that the costs of modifying the theory outweigh the value of retaining it. At that point, you send the theory off to the scrapyard to join your car.
And that brings us back to the Parable. The Parable suggests that the capacity for endless theory modification is a problem with theism in parallel to the theory of the endlessly modifiable gardener. But in fact, this is not a problem at all: rather, as we have seen, it is just a general fact about theories that we can modify them endlessly so long as we have the will to do so.
That leads us into the next question: where does our commitment to keep modifying a theory come from? Well, keep in mind that theories are explanatory frameworks for various facts, evidence, or data. And so, as with our cars, the theory earns its place in our garage for as long as the cost of modifying it is outweighed by the benefit of retaining it.
In the Parable, there is no real consideration of why the believer was so committed to a gardener. On the contrary, the single motivation seems to have been little more than a bit of whimsy upon walking into a forest clearing. And obviously, that is not a sufficient reason to commit to the effort of endlessly modifying a theory. But is theism like that? Is it a theory that is initially proposed for no real good reason at all? Is it all just a bit of whimsy? Not surprisingly, theists don't see it that way. On the contrary, they believe that theism provides a satisfactory explanation of all sorts of things from the existence of a contingent and finely tuned universe to the design of nature, the truth-directedness of our minds, the nature of objective moral value and obligation, and the nature of religious experience. So while it is true that theists often adapt their theistic theory in the light of prima facie disconfirming data, from their perspective the adaptive efforts are indeed justified by the explanatory benefits of their theory. And so, whenever the mechanic's bill must be paid, the theist may be willing to pay it, at least for the time being.
It should be no surprise that most of the people who have defended the Parable as a critique of theism have themselves been sceptics generally of theism and religion. It is also a safe bet that many if not most of them have adhered to a philosophical position known as naturalism. And that brings us to an interesting irony, one that will occupy the remainder of our discussion. It turns out that one can tell a story about naturalism that echoes the story of the Invisible Gardener with a theory undergoing seemingly endless modification.
So what is naturalism? Ask a self-described naturalist, at least one who isn't a professional philosopher, and you will commonly find them saying something like this: ‘I believe that all that exists is natural.’ They may then add, ‘That is, there is no supernatural realm.’ And when asked to explain what they mean, they may then describe a range of entities they reject such as angels, souls, ghosts, and of course, God. Whatever exists, they would insist, is natural.
That's the popular version of naturalism at first blush, and with that we have entered the jungle clearing. But now in our turning of the tables, it is the theist who gets to offer the interrogation and, as we will see, it is the role of the naturalist to offer a constant revision of her thesis that is no less adaptable and ad hoc than any theistic hypothesis, at least from the perspective of the theist. So let's join our parable in progress and in doing so we can relive some of the ways naturalism has been adapted and evolved over the last several decades.
Theist: So everything is natural, huh? And what do you mean by that, exactly? What do all those things you listed – angels, souls, ghosts, and gods – have in common that excludes them from your account of reality?
Naturalist: They are all airy fairy woo.
Theist: Airy fairy woo? Er, can you be more specific?
Naturalist: Okay, I believe that everything that exists is material: it has physical properties like spatial extension and determinate spatial location. All your angels, souls, ghosts, and gods don't have spatial extension or location so they don't exist.
Theist: I see. So then, what about consciousness: you know, the mind? My brain states are physical processes, sure, but it isn't clear at all that mental events like sensations or intentions are physical. Indeed, consciousness seems to be immaterial in its essence.
Naturalist: Maybe, but then the idea actually is that everything is material or that it supervenes on or arises from the material. Consciousness may not be material but in that case it would be an immaterial by-product of the material brain.
Theist: Interesting, this naturalist thesis of yours keeps changing, it seems. But this is getting more curious, for it would seem that on your view consciousness – such as the mental intention to do something – is not part of the causal story. For example, the way you describe it, my intentions to speak a sentence are not part of the causal story of how the sentence gets spoken. Instead, they are nothing more than causally inert foam that rides the waves of my brain's synapses.
Naturalist: You could put it that way, I guess.
Theist: So when I have the intention to utter a sentence, like this sentence right now, my intention isn't actually part of the causal story of how that speech-act was performed? It was just the foam riding the synaptic waves of my brain? Does that make sense? I mean, surely my intention to speak the sentence must play a role in the story of how the sentence was spoken, no?
Naturalist: I'm not sure about that. Look, I don't have the whole mind/brain deal worked out exactly, but I do know this: it will all be explained someday by a future science. Eventually, science will provide the full picture of how all reality fits together and what exists.
Theist: Would you say then that actually naturalism is not so much a statement about what exists as the belief that whatever exists will be described by a hypothetically completed future science?
Naturalist: Huh, now that you put it that way, yes, that sounds right.
Theist: Interesting. So then, I guess it follows that if a hypothetically completed future science should determine that God exists, then you, as a naturalist, should thereby be committed to believing that God exists?
Naturalist: I suppose so. But I don't think that likely at all.
Theist: Likely or not, it turns out that while you initially defined naturalism as entailing the denial of theism, you now say that it is consistent with theism, just so long as theism is ultimately confirmed in a future science. If I may be frank, it seems like your naturalism is endlessly malleable. And it leads me to wonder, what precisely is the difference between this infinitely adaptable theory of naturalism and no naturalism at all?
That quick conversation is not intended to convey the complexity and depth of naturalistic explanations, so if you are a naturalist, please hold your fire. Rather, it is simply to get us to appreciate that naturalism, like theism, can be endlessly adjusted to fit apparently disconfirming data. And if the naturalist keeps making these alterations, it is because she thinks the explanatory benefits of naturalism outweigh the cost of revising the theory.
For that reason, it seems to me that the venerable Invisible Gardener Parable is really a misfire. Whether the theory in question is theism or naturalism or anything else, it doesn't make much sense to criticize people for remaining committed to keeping their theory on the road by adjusting it when the evidence warrants. In each case, the final judgement must be made by proponents of the theory to determine whether the explanatory benefits of the theory continue to outweigh the costs. And it seems to me that in contrast to the IGT, both theism and naturalism are viable theories with clear explanatory value and defensible costs.
