Moving towards a Cartesian Genealogy

René Descartes in his influential book Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences, [Descartes, René. Discourse on the method of rightly conducting the reason and seeking truth in the sciences. [S.l.]: Project Gutenberg Association, 1993], in part, addresses some of the fundamental ways of applying an early formulation of the scientific method. Those who attempt to do genealogical research could well implement some of his methods.

I was early introduced to to Cartesian thought through the study of linguistics. A book influential in my intellectual development, at the time, was Chomsky, Noam. Cartesian Linguistics: A Chapter in the History of Rationalist Thought. New York: Harper & Row, 1966.

Descartes was the originator of what has been termed, "Cartesian Doubt." It is not my intention to apply this in a philosophical sense, but more in the classic scientific methodological sense, that is, to doubt, automatically all knowledge and thereby ascertain what cannot be doubted. Application of this method to genealogy starts with only accepting as proven those facts that are beyond doubt or to put the concept into a legal terminology, accepting those facts that are proven beyond a reasonable doubt.

Why is this necessary? It is a cliché in genealogy that we advance our knowledge of our family history by moving from the known to the unknown. Unfortunately, very often insufficient time and effort are spent in first ascertaining a knowledge of the known before proceeding to extending our investigations to the "unknown." In so doing, the researcher is often accepting as true that which is unproven and even wrong.

Descartes' method can be analyzed into four discrete steps: first, accepting only information you know to be true (beyond a reasonable doubt) or which is not clear and distinct; second, analyzing these truths into smaller more manageable units, that is, taking the information you do have and determining which, if any, of the facts needs further proof, part by part; thirdly, solving the more simple problems first and thereby understanding and thereby, by establishing an order of study (or as the genealogist would say, a to-do list), fourth; complete listing those things that are not yet known, without omission, that require further investigation. I do not go quite so far as Descartes in that I do not hold that proof is necessary not only beyond all reasonable doubt, but beyond all possible doubt.


There is far too much acceptance of unproven information in the genealogical world today. It is literally impossible to build on a false foundation. However, I do recognize that in historical investigations, such as genealogy, sufficient proof may not always be available. Another way of essentially restating this concept can be found in the Genealogical Proof Standard. I refer to the FamilySearch Wiki,

There are five elements to the Genealogical Proof Standard:

1. A reasonably exhaustive search has been conducted.
2. Each statement of fact has a complete and accurate source citation.
3. The evidence is reliable, and has been skillfully correlated and interpreted.
4. Any contradictory evidence has been resolved.
5. The conclusion has been soundly reasoned.

The object of this present analysis is to address is to focus on element number three, the determination of whether the evidence is reliable and has been skillfully correlated and interpreted. In my words, has there been a sufficient foundation laid of evidence that has been proven, to justify an extension of that evidence to further investigation. In this regard, many, many researchers assume that by filling in the few boxes on their genealogy program, they have answered that question in the affirmative.

I will return to an example I have used many times before because of the example's application to this principle. Henry Martin Tanner was born in California in 1852. This is a fact that has been proven, beyond any reasonable doubt. What was never proven, but recorded thousands of times, was where he was born in California. Uniformly, because of a lack of knowledge of the historical fact, his descendants recorded his birth in San Bernardino County which was not formed until 1854.  I will not comment presently on the practice of simply ignoring the issue by omitting the detailed information entirely. I have seen enough Marys born in Ohio in 1850 to last me a lifetime.

To most, this distinction seems picky and trivial, but how many genealogical searches have been terminated unsuccessfully simply by virtue of the fact that information was being sought in the wrong county? In my case, the correct information could only be determined by doubting even the most widely accepted of facts, a fact that that was recorded in published books copied as canonical by the thousands of Tanner descendants.

Now back to Descartes. He said, "I reckoned as well-nigh false all that was only probable. As to other Sciences (including genealogy, my insertion), inasmuch as these borrow their principles from Philosophy (I would say tradition), I judged that no solid superstructures could be reared on foundations so infirm."

Unless there is a stout core of doubters in the genealogical community, there is no hope of moving forward with additional verified information and we will be caught in a cycle of merely copying the errors of all those who failed to doubt in the past or for whatever reason, laziness, perversity or whatever, passed along inaccurate and misleading information. But we must understand that moving from the known to the unknown, requires knowledge of the known.