First, evolution is not a hypothesis, because evolution is not a linguistic entity. It is a process that occurs in nature. Evolutionary theory, on the other hand, is a linguistic entity (it’s a bunch of sentences written in books), which can be either true or false. And, of course, evolutionary theory is true if and only if (iff) it corresponds to the facts that comprise the process of evolution, such as the facts concerning natural selection.
Second, there are no such things as “proven facts.” As we have already seen, only mathematical or logical sentences (and the propositions expressed by them) can be genuinely proven. Empirical theories can only be justified by defeasible reasons, which, however, are often strong enough to warrant treating those theories as reporting the facts correctly. Moreover, facts are not the sort of thing that can be proven. You can’t deduce a fact from some premises, because they are not linguistic entities. What you can do is try to bring about some fact, by acting in various ways (e.g., you could apply antibiotics to bacteria to bring about the evolution of resistance). Or you can discover facts. But you can’t prove them – they are the wrong kind of thing for that.
Finally, what’s the relation between hypotheses and theories? It seems that we often try to use the distinction to mark a difference in how well supported an empirical claim is and how comprehensive its content is. We demand better support for a theory than may be required for a (mere) hypothesis, which is often thought of as something like an educated guess, a conjecture, or a sort of hunch.
If we approach the matter a bit more systematically, we can think of hypotheses as relatively isolated or “stand alone” empirical claims. For example, in scientific modelling, we are often only interested in correctly identifying relations between dependent and independent variables (such as period and length in a pendulum). This can be done regardless of how the resulting model fits together with other things we believe.
When we propose a theory, however, we typically try to fit several hypotheses together into a coherent whole. Recall the earlier example involving the ideal pendulum law. During the process of fitting a curve to the data points you collected, you might think of the result as your hypothesis about how period and length are related. You can then go on and embed this hypothesis into a comprehensive theory or encompassing model, such as the theory of simple harmonic oscillators, or even more broadly, into all of classical mechanics.
“Embedding” means that you try to show how your hypothesis can be derived as a special case of a simple harmonic oscillator or as an instance of Newton’s laws of motion (together with some boundary conditions). Such an embedding also means that the evidence for the other parts of the theory becomes indirect evidence for your original model.
Thus, we can draw the distinction between hypothesis and theory in terms of how many different pieces of information have been integrated, although we have to keep in mind that this distinction is vague.
1.4.1 “It’s True for You but Not for Me”
One topic that often comes up in discussions about truth – a topic we haven’t touched on yet – is that of relativism. Many people profess to be relativists about truth. They might say things such as: “This is true for you but not for me,” or “It was true for Ptolemy that the earth is stationary, but now it is no longer true.” Some might even provide a theoretical defense of the view that truth is relative to one’s culture.
What is often in the background here is the idea that one needs to respect another person’s opinion and perspective. After all, wars have been fought over differences in beliefs. So epistemic humility is a virtue. But this gives rise to a problem. If I disagree with another person, I seemingly need to hold that truth is a matter of opinion, perspective, or culture. However, there is an alternative.
One can respect other people’s opinion and perspective in that one can appreciate how their evidence and cultural experiences might make it seem that so-and-so is the case, while my evidence makes it seem that this is not so. Remember, the defeasibility of our reasons is a sound basis for doubt. The evidence people have access to often varies dramatically among individuals.
It might even be the case that individuals have access to the same body of evidence but give different weights to the various elements based on experience, existing beliefs, practical interests, and cultural values. We’ll explore this possibility in some detail in the next chapter, but for now let’s just say that once we establish the spatiotemporal context (and sometimes the values), we often find that there is little disagreement. Once again, in philosophy as in science, one must take care to make matters clear and, in this case, to not mistake differing interests or perspectives for there being relativistic truth.
Thus, what it is reasonable to believe can vary dramatically from person to person. We have already seen earlier that it can be quite reasonable to believe something that’s false. The evidence one has might in fact not be very good evidence. Thus, I can respect opinions that are different from mine for their reasonableness without having to claim that truth varies from person to person. Once we make a distinction between two ways in which beliefs can be “good” (i.e., their reasonableness and their truth), we can explain variations among what reasonable people believe in terms of differences in evidence without having to be relativists about truth.
And that is a good thing, because relativism about truth is ultimately indefensible. Take, for example, the sentence, “There is no objective truth.” Is that sentence itself true? If it is objectively true, then it has just refuted itself. If it is merely relativistically true, then why should I, who believes in objective truth, be moved by it? Subscribing to relativism about truth puts one into a really bad intellectual (and practical!) position.
Of course, these remarks are far from sufficient for putting relativism to rest. There are fairly sophisticated defenses of this position, but it would lead us too far into epistemology proper to give them a fair hearing. What the remarks do show, however, is that relativism as a knee-jerk reaction to the existence of disagreements about truth is simply too naïve.
1.4.2 Perspectivism
Although relativism, at least in its unsophisticated form, is not a plausible response to disagreements about what is true, there is a viable approach that allows for the truth of multiple claims about the world, but not the truth of every claim as relativists would contend. Ronald Giere advocated for scientific perspectivism, a philosophical position mediating between the hard-driving objectivism of most scientists (as well as the unyielding realism of many philosophers of science), and the “anything goes” constructivism found among postmodern social scientists and humanists. Perspectivism contends that while there is an objective reality, our statements about its features are always made from a particular viewpoint (both literally and figuratively) and are hence partial truths, at best. This position fundamentally differs from relativism in that once a perspective is chosen, claims about the natural world can be empirically tested and refuted or confirmed.
The notion that truth claims are always relative to a perspective is, as Giere points out, not radical. Even the staunchest empiricists cannot escape the fact that scientific claims are relative to language. What Giere initially proposed was to extend linguistic contextualization to one’s physical position (both in relation to the object of study and the internal processing of the incoming signal).
Consider, for example, a biologist who asserts that the petals of a particular flower are white. One need only look to see that this is true. However, suppose another biologist comes along with a device which reveals ultraviolet reflectance, looks through this instrument at the flower, and declares that it is striped. And, in fact, some flowers have so-called “bee guides” that direct bees, which can see in the ultraviolet, to the stamen and nectary which provide pollen and nectar. Which description of the flower is true? The perspectivist would respond
