Let me start this discussion with a conversation that I’ve had with a large handful of skeptics. It goes a little like this:
Me: God exists!
Skeptic: Give me evidence!
Me: The cosmological argument, the teleological argument, the minimal facts argument for the resurrection of Christ, and here’s a blog post where I discuss why I’m a Christian.
Skeptic: No, I said I wanted evidence.
Me: I just gave you a bunch of evidence.
Skeptic: An argument is not evidence.
And suddenly, we reach an impasse. The skeptic is unwilling to analyze an argument for God’s existence, even though he asked for evidence. The conversation has now shifted from the evidence for God’s existence to the question, “What is evidence?”
Let’s dive in.
It’s always good to start with definitions.
What is “Evidence?”
There are a lot of really interesting articles on the nature of evidence, but let’s look at three reliable sources.
- The Internet Encyclopedia of Philosophy has a really interesting article, check it out. In an epistemological sense, evidence is considered to play a role in justification for a particular belief.
- Dictionary.reference.com defines evidence as “that which tends to prove or disprove something; ground for belief; proof.”
- Oxforddictionaries.com defines evidence as “the available body of facts or information indicating whether a belief or proposition is true or valid.”
All of this together should give us a usable, uncontroversial definition of the word evidence. Evidence can be defined as the available body of facts or information which tends to prove or disprove something, usually associated with the justification for beliefs. That definition of evidence seems to fit well with the three references used above, as well as our everyday understanding of evidence. We could get a lot deeper into this discussion (obviously), but it is not necessary for the goal of this post.
What is an Argument?
Now that we know what evidence is, what is an argument? The discussion on the nature of arguments is equally (or possibly more) complex than the discussion of evidence, but we’re not going to go deeper than we have to. And, for the sake of consistency, I’ll use the same three sources.
And, as a point of note, I am using the term argument in its technical sense—not synonymous with bickering or quarrelling.
- The Internet Encyclopedia of Philosophy has, again, a very interesting article on arguments. I’d encourage you to read it. Put very briefly, an argument is “a collection of truth-bearers … some of which are offered as reasons for one of them, the conclusion” and “a typical use of an argument is to rationally persuade its audience of the truth of the conclusion.”
- Dictionary.reference.com defines an argument as “a statement, reason, or fact for or against a point.”
- OxfordDictionaries.com defines an argument as “a reason or set of reasons given in support of an idea, action or theory.”
All of this together should give us a usable, uncontroversial definition of the word “argument”. An argument can be defined as a collection of truth-bearing statements, reasons or facts used in support of an idea, theory or belief. Arguments are used to rationally persuade its audience of a particular conclusion. Just like my definition of evidence, the discussion of arguments can go much deeper than this. But for the goal of this post, this definition works well.
Given the two definitions above, both arguments and evidence deal with coming to conclusions (either affirming or denying something). They both also deal with supporting beliefs, and they both deal with reasons and facts.
So what is the difference?
It looks like the definitions of evidence and arguments overlap in all the important categories, except one. Arguments deal with “truth-bearers” (a term used by the IEP), which are statements, beliefs, or propositions that can either be true or false.
For example, the statement “all men are mortal” is either true or false. The same goes with the statement “Elijiah is a man.”
So an argument is a series of truth-bearers that lead to a conclusion. Take the two examples I used above. From those two statements, what conclusion can be reached?
- All men are mortal.
- Elijiah is a man.
- Therefore, Elijiah is mortal.
We have good evidence to believe the 1st statement. And, considering I am the Elijah spoken of in the second premise, we have good evidence to believe that I am a man. And, therefore, following the rules of logical inference, we have evidence to believe the conclusion that: I am mortal.
*side note – how logic works*
In order for a conclusion to logically follow from an argument, the argument must be both valid and sound. Not all arguments are sound and/or valid. An argument is valid only when its form follows the rules of logic (does not commit a logical fallacy). An argument is sound when it is valid and all of its premises are true.
An argument is a collection of truth-bearers that when taken to their logical conclusion, give evidence for a particular conclusion. If there is good evidence to accept the premises, there is, therefore, good evidence to accept the conclusion.
Take the syllogism offered earlier.
- All men are mortal.
- Elijiah is a man.
- Therefore, Elijiah is mortal.
Wouldn’t you say that you now have evidence that I (Elijiah) am mortal? Or, do you still have to kill me (or wait for me to die) to know that I am mortal? It seems obvious that you have good evidence to believe that I am mortal, wholly apart from killing me. And this evidence comes because of the combination of the evidence for the premises as well as the logical structure of the argument.
Evidence can be defined as the available body of facts or information which tends to prove or disprove something…
An argument can be defined as a collection of truth-bearing statements, reasons or facts used in support of an idea, theory or belief…
Then it seems reasonable to conclude that when an argument is both valid and sound, it becomes evidence for a particular conclusion. So is an argument actually evidence?
It would seem that the answer is… yes.
Important point to note:
If the argument is unsound, it cannot be considered evidence.
If the argument is invalid, it cannot be considered evidence.
This is important for both sides of the theism debate to understand. For the theist, the arguments for God’s existence are, in fact, evidence for God’s existence (assuming logical soundness and validity, of course). But on the flip side, this works out for the atheist as well. Many atheists appeal to arguments (such as the problem of evil) in order to make the case against God’s existence. If the problem of evil succeeds, it is evidence against God’s existence.
I know, this is getting long. I have one more point to make, promise!
I would like to take this opportunity to elaborate on the point a bit, and make an even stronger point. Not only is an argument evidence, but an argument is oftentimes required when discussing the reasons to believe a certain thing. If your friend says, “I have a red 2016 Maserati,” it is not unreasonable to ask for evidence. If she shows you her beautiful car, then you have evidence for her claim.
But not everything is this simple. A lot of times, a logical inference is essential for proper reasoning.
Take common descent for example.
One of the many evidences presented for common descent is homology. We have direct experience (empirical evidence) with structures that are similar. However, if we just look at the direct observation or experience, we don’t actually have evidence for common descent. And this is because similar structures are evidence for similar structures. That’s it.
In order to say that it is evidence for common descent, there must be a logical flow of thought; something that connects the ‘direct observation’ to common descent. So an argument must be constructed that shows how homology can lead us to conclude the truth of common descent.
Another example would be the age of the earth (yes, I am an ‘old earther’).
We have quite a bit of good evidence for the age of earth. I would imagine many of you would agree. However, this evidence is almost exclusively in the form of a valid and sound argument.
Think about it. We have rocks/meteorites and radioisotope data, right? But exactly how do we get from looking at the rocks to the 4.5 billion year old earth? Well, we take what we know about the decay rates of radioisotopes, factor in potential variables, calculate the half-life of a particular isotope, etc. Much like my common descent example, we must rely on valid inferences; there must be a logical flow of thought that connects the ‘direct observation’ to the age of the earth.
For both evolution and the age of the earth, we rely on valid and sound arguments as evidence to support a particular propositions. We may not always explicitly state our arguments for these things in modus ponens, but there is an argument there. Without it, we wouldn’t actually have evidence for evolution or the age of the earth.
Much of what we have evidence for/against is a combination of empirical evidence and logical inference towards/away from conclusion.
To conclude, here is my recommendation.
Don’t just assert that you need direct, physical evidence for something. Examine the reasons for believing something, and do your best to consider the evidence presented. Often times, expecting a specific type of evidence will force you into being inconsistent in examining evidence for different things.
Feel free to leave comments or questions below, and thanks for reading.