The Makedonian phalanx -- why such depth?

[Paralus]

Always with the negative waves. Enough with the negarive waves Moriarty

If there is some anomaly regarding depth of phalanxes that you feel can't be explained by my hypothesis/interpretation of what information we have, please point to it and I shall endeavour to explain, or else concede the hypothesis fails ! [...]

As to Mantinea, I see nothing in the descriptions of that battle which go against the functioning of the phalanx that I have postulated......

I had posted those “anomalies” in my previous post. There is, according to Thucydides, no uniformity of depth to the Spartan files. And it is files – as you say – that matter here. It follows there can be “closing down” from 8 to four if those files are between 5 and 9 or more deep.

Further Thucydides explicitly states that the Brasideans and Sciritae are ordered to remove themselves further to the left – whole units – so as to avoid flanking. As well, whole units (companies) are to be transferred into the resulting gap from the right wing. When this fails to occur the Brasideans and Sciritae do not have time to fill up the gap. These movements are by whole units in battle order

No, but possibly every Greek, certainly the educated citizens of a poleis, knew how a phalanx moved and fought, since it hadn't changed fundamentally in hundreds of years. Most of these would not, for example, have seen a Macedonian sarissa armed phalanx in action, hence Polybius' vivid descriptions. Remember that the old citizen militias of the city-states had gone by Polybius' time, and military forces consisted largely of professionals,....

To quote a famous individual:

It is you that say it.

Well, indeed. And citizens who have not ever seen a phalanx in action then need to have the workings of that phalanx explained to them. As Polybios does – in detail – all except for that all important keystone in the arch of your argument: that the phalanx always adopted close order by doubling down from sixteen to eight. This, apparently, of all the details can be assumed.

The argument from that silence is not compelling.