She’ll wear a grue dress

This is a continuation of the articles “She wore a blue dress” and “Rescuing the Excluded Middle“, which introduced crisp imprecision and fuzzy uncertainty. The former being evaluative and the latter both subjective and contextual. The articles discuss, relate, and sometimes further the formalization of transitional modeling, so they are best read with some previous knowledge of this technique. An introduction can be found starting with the article “What needs to be agreed upon” or by reading the scientific paper “Modeling Conflicting, Unreliable, and Varying Information“. In this article I will discuss the effect of a chosen language upon the modeling of posits, with particular homage to the new riddle of induction and Goodman’s predicate ‘grue’.

In order to look at the intricacies of using language to convey information about the real world, we will focus on the statement “She’ll wear a grue dress”. First, this refers to a future event, as opposed to the previously investigated statement “She wore a blue dress”, which obviously happened in the past. There are no issues talking about future events in transitional modeling. Let’s say Donna is holding the dress and is just about to put it on. She would then, with absolute certainty, assert the posit “She’ll wear a grue dress”. It may be the case that the longer time before the dress will be put on, the less certain Donna will be, but not necessarily. If she just after New Year’s Eve is thinking of what to wear at the next, she could still be certain. Donna could have made it a tradition to always wear the same dress.

There is a difference between certainty and probability. If Donna is certain she will wear that dress at the next New Year’s Eve, she is saying her decision has already been made to wear it, should nothing prevent her from doing so. From a probabilistic viewpoint, lots of things can happen between now and New Year preventing that from ever happening. The probability that she will wear the dress at next New Year’s Eve is therefore always less than 1, and will be so for any prediction. Assuming the probability could be determined, it would also be objective. Everyone should be able to come up with the same number. Bella, on the other hand, could be certain that Donna will not wear the dress at the next New Year’s Eve, since she intends to ruin Donna’s moment by destroying the dress. Certainty is subjective and circumstantial. I believe this distinction between certainty and probability is widely overlooked and the concepts confused. “Are you certain? Yes. Is it probable? No” is a completely valid and non-contradictory situation.

With no problems of talking about future events, let’s turn our attention to ‘grue’. Make note of the fact that you would not have reacted in the same way if the statement had been “She’ll wear a blue dress”, unless you happen to be among the minority already familiar with the color grue. If you belong to that minority, having studied philosophy perhaps, then forget for a minute what you know about grue. I will look at the word ‘grue’ from a number of different possibilities, of only the last will be Goodman’s grue.

What is grue?

  1. It is a color universally and objectively distinguishable from blue.
  2. It is a color selectively and subjectively indistinguishable from blue.
  3. It is a synonym of blue.
  4. It is an at the current time widely known color.
  5. It is an at the current time little known color.
  6. It is an at the current time unknown color that will become known.
  7. It is an at the current time known color synonymous with blue that at some point in the future will be considered different from blue (Goodman).

In (1) there will likely be no issues whatsoever. Perhaps there is a scientific definition of ‘grue’ as a range of wavelengths in between green and blue. On a side note and right now, the color greige is quite popular and a mix between grey and beige. Using that definition of ‘grue’ anyone should be able to reach the same conclusion whether an actual color can be said to be grue or not. Of course most of us do not possess spectrophotometers or colorimeters, so we will judge the similarity on sight. If enough reach the same conclusion, we may say it’s as close to an objectively determinable color as we will get. This is good, and not much thought has to go into using >grue< in a posit.

In (2) there may be potential issues. Perhaps grue and blue become indistinguishable under certain conditions, such as lighting, or let’s assume that 50% of the population cannot distinguish between grue and blue because of color blindness. Given two otherwise identical dresses of actual different colors, grue and blue, they may assert that she wore or will wear both of these, simultaneously. Such assertions can be made in transitional modeling and possible contradictions found using a formula over sums of certainty (see the scientific paper). To resolve this, non-contradiction either needs to be enforced at write time or periodically analyzed. Unknown types of color blindness could even be discovered this way, through statistically significant contradictory opinions. That being said, one should document already known facts and new findings with respect to effects that may disturb the objectivity of the values used.

In (3) there is a choice or a need for documentation. Either one of ‘blue’ and ‘grue’ is chosen and used consistently as the value or both are used but the fact that they are synonymous is documented. This may be a more common situation than one first may think, since ‘grue’ could be the word for ‘blue’ in a different language. This then raises the question of synonymy. What if there are language-specific differences between the interpretations of ‘grue’ and ‘blue’, so that they nearly but not entirely overlap? If grue allows a bit more bluegreenish tones than blue then they are only close to synonymous. This speaks for keeping values as they were stated, but that values themselves then may need their own model.

With those out of the way, let us look at how well known of a color grue is. In (4) almost everyone has heard of and use grue when describing that color. This is good, both those who are about to assert a posit containing >grue< will know how to evaluate it, and those later consuming information stored in posits will understand what grue is. With (5) difficulties may arise. In the extreme, I have invented the word ‘grue’ myself and nobody else knows about it. However, when interrogated by the police to describe the dress of the woman I saw at the scene of the crime, I insist on it being grue. No other color comes close to the one I actually saw. Rare values, like these, that likely can be explained in more common terms need translation. If done prescriptively the original statement is lost, but if not, it must be done descriptively at the cost of the one consuming posits first digesting translation logic. This is a very common scenario when reading information from some system, in which you almost inevitably find their own coding schemes, like “CR”, “LF”, “TX”, and “RX” turning out to have elaborate meanings.

Now (6) may at first glance seem impossible, but it is not. Let us assume that we believe the dress is blue and the posit temporally more qualified to “She’ll wear a blue dress on the evening of December 31st 2020”. Donna asserts this with 100% certainty the day after the preceding New Year’s Eve. When looking at the dress on December 31st 2020, Donna has learnt that there is a new color named grue, and there is nothing more fitting to describe this dress. Given this new knowledge, that the dress is and always has been grue, she retracts her previous posit, produce a new posit, and asserts this new one instead. The process can be schematically described as:

posit_1     = She'll wear a blue dress on the evening of December 31st 2020

assertion_1 = Donna, posit_1, 100% certainty, sometime on January 1st 2020

assertion_2 = Donna, posit_1, 0% certainty, earlier on December 31st 2020

posit_2     = She'll wear a grue dress on the evening of December 31st 2020

assertion_3 = Donna, posit_2, 100% certainty, earlier on December 31st 2020

Given new knowledge, you may need to correct yourself. This is precisely how corrections are managed in transitional modeling, in a bi-temporal solution, where it is possible to deduce who knew what when. This works for rewriting history as well:

posit_3     = The dress is blue since it was made on August 20th 2018

assertion_4 = Donna, posit_3, 100% certainty, sometime on August 20th 2018

assertion_5 = Donna, posit_3, 0% certainty, earlier on December 31st 2020

posit_4     = The dress is grue since it was made on August 20th 2018

assertion_6 = Donna, posit_4, 100% certainty, earlier on December 31st 2020

The dress is and always has been grue, even if grue was unheard of as a color in 2018. Nowhere do the posits and assertions indicate when grue started to be used though. This would, again be a documentation detail or alternatively warrant explicit modeling of values.

Finally there is (7), in which there is a point in time, t, before which we believe everything blue to be grue and vice versa. Due to some new knowledge, say some yet to be discovered quantum property of light, those things are now split into either blue or grue to some proportions. This is really troublesome. If some asserters were certain “She wore a blue dress” and others were certain “She wore a grue dress”, in assertions made before t, that was not a problem. They were all correct. After that point in time, though, there is no way of knowing if the dress was actually blue or grue from those assertions alone. If we are lucky enough to get hold of the dress and figure out it is blue, things start to look up a bit. We would know which asserters were wrong. Their assertions could be invalidated, while we make new ones in their place. In the less fortunate event that the dress is nowhere to be found, previous assertions could perhaps be downgraded to certainties in accordance with the discovered proportions of blue versus grue.

The overarching issue here, which Goodman eloquently points out, is that this really messes up our ability to infer conclusions from inductive reasoning. How do we know if we are in a blue-is-grue situation soon to become a blue-versus-grue nightmare? To me, the problem seems to be a linguistic one. If blue and grue have been used arbitrarily before t, but after tsignify a meaningful difference between measurable properties, then reusing blue and grue is a poor choice. If, on the other hand, blue and grue were actually onto something all along, then this measurable property must have been present and in some way sensed, and many assertions likely to be valid nevertheless. This reasoning is along the lines of philosopher Mark Sainsbury, who stated that:

A generalization that all A’s are B’s is confirmed by instances unless we have good reason to believe that there is some property, O, such that every A-instance is O, and if those A-instances had not been O, they would not have been B.

In other words, some additional property is always hiding behind issue number (7).

With all that said, there are a lot of subtleties concerning values, but most, if not all of them can be sorted out using posits and assertions, with the optional addition of an explicit model of values, together with prescriptive or descriptive measures. That being said, if language is used with proper care and with the seven types of ‘grue’ mentioned above in mind, you will likely save yourself a lot of headaches. We also learnt that people normally think in certainties rather than probabilities.

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Lars Rönnbäck

Co-developer of the Anchor Modeling technique. Programmer of the online modeling tool. Site maintainer. Presenter and trainer.

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