The Fugue

From time to time I think about evidence-based genealogy. All good genealogy is evidence-based, i.e. you have evidence to support all of your conclusions, and a complete stranger would agree with your conclusions because of your evidence. But most amateur genealogists, and computer software, treat evidence as a secondary concern at best. To them, it's the conclusions that are important, and documenting the evidence is an afterthought and a bother and usually is not done at all. After all, it's obvious at the moment that you're recording the marriage of Fred and Wilma that it's true. Of course later we find that Fred and Wilma never even knew each other, and we've forgotten why we thought they got married. Oops.

The problem is exacerbated by the fact that most amateur genealogists (including genealogy software developers) start out by recording the family history stored in their heads. This is information that they are as sure about as they are of gravity. Recording evidence of these "givens" is tedious and ridiculous. And there's enough of it that by the time you've entered it all into the computer (or onto family group sheets) you have developed a solid bad habit of not entering sources.

This is compounded even further by genealogical databases. Go to a family history center or genealogy website and download a few thousand or tens of thousands of names. Who would turn down such a tremendous head start? Who would meticulously verify and document the evidence of every one of those names and the dozen or more conclusions associated with each one?

But I'm getting sidetracked. The question of the day is whether genealogy is an inductive or deductive sport. Let's review the definitions.

induction |inˈdək sh ən|, noun. The inference of a general law from particular instances.

deduction |diˈdək sh ən|, noun. The inference of particular instances by reference to a general law or principle.

So induction is going from specific to general, i.e. making conculsions based on evidence. Sounds like genealogy, right? But if we replace "general law or principle" with the word "premise," then it also looks a lot like genealogy. The problem is, neither evidence nor genealogical conclusions look an awful lot like "general laws."

Let me take another crack at defining the terms. Induction is when you take a bunch of observations and induce a probable generality from them. Deduction is when you take premises and deduce an absolute generality from them, given that the premises are true.

If I have a birth certificate for one Fred Flintstone, then I can deduce that some Fred Flintstone was born on such and such date. The only way to question that conclusion is to question the veracity of the birth certificate. Note that I said some Fred Flintstone. A common pitfall in genealogy is the leap from evidence for someone of the same name to evidence for the particular person being researched.

If I have the birth certificate, and a bunch of other documents, and they all support the notion that there was one Fred Flintstone in Bedrock during this period of time, and all the evidence fits together well, I can construct a probable picture of the person Fred Flintstone. This seems to be induction. Even though my premises are true, I may be taking a leap of faith to conclude that the Fred Flintstone from the birth certificate is the Fred Flintstone that married Wilma (and therefore my ancestor). It's not deduction because it doesn't follow directly from the premises.

Well, so it seems like genealogy is both inductive and deductive, and that's before you even consider the fallability of evidence. No wonder it can be such a mess. This underlines the need for tools that help us dwell in the realm of evidence which is relatively stable compared to the realm of conclusions. Very rarely indeed will a primary source be completely false (though it is more common to find inaccurate sources—bad spelling or slightly-off dates). More often, our conclusions based on the primary sources are completely false. Yet, in the end, it's the conclusions that we care about. So the software needs to allow us to dwell in the evidence world while providing the context of our current set of conclusions.

Software developers would be tempted to treat evidence-based genealogical software as deductive reasoning. They'd program in all kinds of ways for the computer to do the thinking for you. Fuzzy probable conclusions have no place in this vision. I think that's the point of this post. We mustn't fall into that trap or we'll have another dark age like the conclusion-based age we're still struggling to get out of. Except this one will be worse because it doesn't even match the amateur genealogist's first way of thinking of things.

While I believe there is room for computers to automatically infer things based on evidence, and direct researchers to areas of the family tree that may be influenced by this new bit of information, I think it is vital that we not lose sight of the fact that this is a human enterprise. In the end, a person must interpret the evidence, and she must be able to easily change her mind later. As such, the software must first and foremost be an organizational tool. It must help us make sense of the mass of evidence and conclusions. It must free us from the shackles of disorganization without binding us with the shackles of inflexible deductive logic. And yet, at best it will encourage the infallibility of deductive reasoning where appropriate.

So what do you think? I'm a computer scientist, not a logician and I have been known to confuse inductive and deductive reasoning. Is genealogy inductive, deductive, or both?