Simplicity as Evidence of Truth: Theories Tying Into Background Knowledge

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This part 2 of a series on simplicity being evidence of truth.

1. Simplicity as Evidence of Truth: Justifying Ockham’s Razor
2. Simplicity as Evidence of Truth: Theories Tying Into Background Knowledge
3. Simplicity as Evidence of Truth: How Do We Know It?

As mentioned in part 1, much of this series is taken from Richard Swinburne’s Simplicity as Evidence of Truth. This article will discuss how simplicity plays a role in judging how well a theory fits in with our background knowledge. Before moving on I’ll introduce some preliminaries.

Some Facets of Simplicity

In this article it’ll be nice to mention a few facets of simplicity borrowed from Swinburne.[1]

1. Number of entities. The theory that postulate fewer entities is simple than if it postulated more entities. As Swinburne notes, “The application of this facet in choosing theories is simply the use of Ockham’ razor.”[2]
2. Number of kinds of things. A theory that postulates fewer different kinds of entities is simpler than if it postulated many different kinds of entities, e.g. a theory that postulates fewer different kinds of quark is simpler than a theory that postulates more of them.
3. Fewer separate laws is simpler than many separate laws.

More could be listed (and Swinburne does list more) but this small list will be enough for our purposes.

Simplicity Not the Only Factor

I’ve been using the phrase “ceteris paribus” an awful lot in this series precisely because there are other factors to consider when choosing a good explanation besides simplicity. The list below is largely taken from Richard Swinburne.[3]

• Yielding the data. This category covers both explanatory scope (how much data the theory explains) and explanatory power (the probability of expecting the data if the explanation were true).
• Content. All else held constant, the theory that makes more claims (or is a stronger claim in the sense that it “claims more”) is less likely to be true than one that makes fewer claims (or is a weaker claim in the sense that it “claims less”). For example, “At least a million animals of this species have black fur” is a stronger claim than “At least ten animals of this species have black fur.” All else held constant, the weaker claim “At least ten animals of this species have black fur” is more likely to be true than the stronger claim.
• Fitting in with background knowledge. For example, “The hypothesis that John stole the money is rendered more probable if we know [due to our background knowledge] that John has stolen on other occasions and comes from a social group among whom stealing is widespread.”[4] The likelihood of such background beliefs being true plays a role in our judgments. However, simplicity has a role when determining how well a theory fits in with our background knowledge.

And it’s that last item that we’ll deal with next in regards to simplicity.

Simplicity and Background Knowledge

Where there is relevant background knowledge, simplicity is a factor that determines which theory “fits best” with such data. Swinburne even goes so far as saying that “fitting better” is “fitting more simply” and making for a simpler overall view with the world.[5] When discovering a new chemical substance, it’s possible that it has a special kind of quark or special kind of chemical bond never before discovered that yields the same data, but it’s simpler not to posit “more than one kind of thing” and simply use what’s available ceteris paribus. Notice that in this case having a special kind of quark or special kind of chemical bond never seen before does tie in with our background knowledge to some extent (we believe that there are such things as quarks and chemical bonds) but fitting into our background knowledge more simply (using the same sort of quarks and chemical bonds we know of) is the better option. Simplicity is clearly a role when deciding how well a theory fits in with our background knowledge.

Theories often interact with each other; our current theory of genetics ties in with belief in DNA, and the belief that DNA ties in with belief in atoms etc. Also, when making predictions we rely on background knowledge; e.g. at one point people thought that if the earth was really moving, birds would be blown West when they let go of a tree branch. We no longer accept that as evidence that the earth is not moving because we have a different background system of physics that allows us to make different predictions. Call this network of theories and assumptions a conceptual grid. When looking into what theories tie into our background knowledge, we are assuming that ceteris paribus the world is more likely to be simple than complex, and ceteris paribus we prefer simpler conceptual grids to complex ones. Hence when discovering a new chemical, we don’t assume the chemical has entirely new types of quarks (thus giving us a more complex conceptual grid) when the chemical having the same sort of quarks we are familiar with will do (in terms of yielding the data etc.).

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[1] Swinburne, Richard. Simplicity as Evidence of Truth (Milwaukee, Wisconsin: Marquette University Press, 1996), pp. 29-30, 31.

[2] Swinburne, Richard. Simplicity as Evidence of Truth (Milwaukee, Wisconsin: Marquette University Press, 1996), p. 29

[3] Swinburne, Richard. Simplicity as Evidence of Truth (Milwaukee, Wisconsin: Marquette University Press, 1996), pp. 18-19

[4] Swinburne, Richard. Simplicity as Evidence of Truth (Milwaukee, Wisconsin: Marquette University Press, 1996), p. 18

[5] Swinburne, Richard. Simplicity as Evidence of Truth (Milwaukee, Wisconsin: Marquette University Press, 1996), p. 45