Ashby’s Trowel:

In today’s post, I am looking at a concept that I am referring to as Ashby’s trowel. The premise of this idea is very simple – context matters! I will start off the discussion using the very well-known heuristic of Occam’s razor. Occam’s razor, named after the 14th century English Franciscan friar, William of Occam. This is commonly described as – entities should not be multiplied beyond necessity. In other words, explanations should only have the necessary number of assumptions. Very often this is incorrectly presented as a call to seek simplicity. As a cybernetician, I can tell you that simplicity is overrated.

The idea of a philosophical razor is that it can be used to remove the unwanted things by slicing the unwanted assumptions away from the model. Occam’s razor is the most famous of the many philosophical razors. In medicine, Occam’s razor is often contrasted with Hickam’s dictum. Hickam’s dictum is named after the twentieth century American physician, John Hickam. It is described as – patients can have as many diseases as they damn (or darn) well please. So, if an elderly patient complains of several ailments, Hickam would advise that we trust the patient and try to treat several likable diseases instead of assuming that the different ailments are resulting from one single disease. This heuristic is meaningful when the patient is elderly, is on multiple medications, and if the ailments started at different times. In other words, simplicity is overrated when dealing with a complex situation as our human bodies, especially when tackled with age and side effects of many different medications.

A trowel is a tool used by a mason to add and to remove mortar as needed so that a clean level surface is achieved. With Ashby’s trowel, I am putting forth the reminder that the solution that you are seeking should have enough complexity to match the complexity of the problem that you are seeking to solve. Ashby presented this as his law of Requisite Variety – only variety can absorb variety. Here variety refers to the number of possible states of a “system” conjured up (constructed) by an observer. If we take the example of a light switch, it generally has two states – ON and OFF. Thus, its variety is 2. The external variety is always more than the internal variety. In the case of a light switch, the user’s variety of needing something ON and OFF when they want, can be easily met by the light switch. But now consider if the user wants to dim the lighting with the switch. The variety of ON and OFF cannot meet this new demand that is added by the user. The Engineer now has to come up with a dimmer switch that has indefinite variety between its LOW and HIGH setting.

When we have a problem, we are often reminded to go for simple solutions. This may be a good heuristic to hold on to, however this should not be the law. One of the problems with seeking simple solutions is that we stop searching for more solutions once we get to a “simple” solution. This is referred to as the “satisfaction of search.”

From the cybernetics standpoint, simplicity and complexity also depend upon who is doing the observing. What is simple to you may be complicated for me, and vice versa. The more meaningful heuristic to have is Ashby’s trowel – context matters, so we have to match the complexity.

I welcome the reader to look into this more –

I will finish with a wise quote that is very much aligned to Ashby’s trowel, from one of my favorite philosophers, David Hume – If the cause, assigned for any effect, be not sufficient to produce it, we must either reject that cause, or add to it such qualities as will give it a just proportion to the effect.

Stay safe and always keep on learning…

In case you missed it, my last post was The Purpose of Purposeful Entities in Purposive Systems:

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