“The unquantified life is not worth living.”
While quantifying one’s life is an old idea, using devices and apps to quantify the self is an ongoing trend. As a runner, I started quantifying my running life back in 1987, which is when I started keeping a daily running log. Back then, the smartest wearable was probably a Casio calculator watch, so I kept all my records on paper. In fact, I still do, as a matter of tradition.
I use my running log to track my distance, route, time, conditions, how I felt during the run, the number of times I have run in the shoes and other data. I also keep a race log and a log of my weekly mileage. So, like Ben Franklin, I was quantifying before it became cool. Like Ben, I have found this useful. Looking at my records allows me to form hypotheses about what factors contribute to injury (high mileage, hill work and lots of racing) and what results in better race times (rest and speed work). As such, I am sold on the value of quantification, at least in running.
In addition to my running, I am also a nerdcore gamer. I started with the original D&D basic set and still have shelves (and now hard drive space) devoted to games. In these games, such as Pathfinder, D&D, Call of Cthulu and World of Warcraft the characters are fully quantified. That is, the character is a set of stats such as Strength, Constitution, Dexterity, hit points, and Sanity. These games also have rules for the effects of the numbers and optimization paths. Given this background in gaming, it is not surprising that I see the quantified self as an attempt by a person to create, in effect, a character sheet for themselves. That way they can see all their stats and look for ways to optimize. As such, I get the appeal. As a philosopher I do have concerns about the quantified self and how that relates to the qualities of life, but that is a matter for another time. For now, I will focus on a brief critical look at the quantified self.
Two obvious concerns about the quantified data regarding the self (or whatever is being measured) are questions regarding the accuracy of the data and questions regarding the usefulness of the data. To use an obvious example about accuracy, there is the question of how well a wearable, such as a smart watch, really measures sleep. In regard to usefulness, I wonder what I would garner from knowing how long I chew my food or the frequency of my urination.
The accuracy of the data is primarily a technical or engineering problem. As such, accuracy problems can be addressed with improvements in the hardware and software. Of course, until the data is known to be reasonably accurate, then it should be regarded with due skepticism.
The usefulness of the data is a somewhat subjective matter. That is, what counts as useful data will vary from person to person based on their needs and goals. For example, knowing how many steps they take at work would probably not be useful to an elite marathoner. However, someone else might find such data very useful. As might be suspected, it is easy to be buried under an avalanche of data and a challenge for anyone who wants to make use of the slew of apps and devices is to sort what would be useful in the thousands or millions of data bits they might collect.
Another concern is the reasoning applied to the data. Some devices and apps supply raw data, such as miles run or average heartrate. Others purport to offer an analysis of the data, to engage in automated reasoning. In any case, the user will need to engage in some form of reasoning to use data.
In philosophy, the two basic tools used in personal causal reasoning are derived from Mill’s classic methods. One is the method of agreement (or common thread reasoning). Using this method involves considering an effect (such as poor sleep or a knee injury) that has occurred multiple times (at least twice). The idea is to consider the factor or factors that are present each time the effect occurs and to sort through them to find the likely cause (or causes). For example, a runner might find that all her knee issues follow extensive hill work, thus suggesting the hill work as a causal factor.
The second method is the method of difference. Using this method requires at least two situations: one in which the effect has occurred and one in which it has not. The reasoning process involves considering the differences between the two situations and sorting out which factor (or factors) is the likely cause. For example, a runner might find that when he does well in a race, he always gets plenty of rest the week before. When he does poorly, he is consistently tired due to lack of sleep. This would indicate that there is a connection between rest and race performance.
There are, of course, many classic causal fallacies that serve as traps for such reasoning. One of the best known is post hoc, ergo propter hoc (after this, therefore because of this). This fallacy occurs when it is inferred that A causes B simply because A is followed by B. For example, a person might note that her device showed that she walked more stairs during the week before doing well at a 5K and uncritically infer that walking more stairs caused her to run better. There could be a connection, but it would take more evidence to support that conclusion.
Other causal reasoning errors include the aptly named ignoring a common cause (thinking that A must cause B without considering that A and B might both be the effects of C), ignoring the possibility of coincidence (thinking A causes B without considering that it is merely coincidence) and reversing causation (taking A to cause B without considering that B might have caused A). There are, of course, the various sayings that warn about poor causal thinking, such as “correlation is not causation” and these often correlate with named errors in causal reasoning.
People vary in their ability to use causal reasoning, and this would also apply to the design of the various apps and devices that purport to inform their users about the data they gather. Obviously, the better a person is at philosophical (in this case causal) reasoning, the better they will be able to use the data.
The takeaway, then, is that there are at least three important considerations regarding the quantification of the self in regards to the data. These are the accuracy of the data, the usefulness of the data, and the quality of the reasoning (be it automated or done by the person) applied to the data.

One interesting narrative about the riots in Baltimore involved the concept of the rule of law. Put roughly, the rule of law is the idea that the law should govern rather than the arbitrary decisions of those in power. The notion is sometimes applied to the citizens as well, that citizens should follow the rule of law to resolve conflicts—as opposed to engaging in activities such as riots or vigilantism.