One very important aspect obviously is what you may call the social archaeology, the social subsystem, and it was clear that this was the time in the Aegean that you begin to see evidence for people of high status reflected partly in the burials where you get metal objects and sometimes silver objects, gold objects even in some of the graves. In Troy, Troy II, it's the same period, you get the great hoards that Schliemann found, or allegedly found, including golden and silver vessels and so on. And I began to see how you could tell the story of the rise of civilisation, the rise of complex society in the Aegean using the local evidence and not telling it as a story of how wisdom came from the Near East and there wasn't that much contact with the Near East at that time anyway, but how you could see it in terms of the inter-relations that developed within the Cyclades and between the Cyclades and Crete and mainland Greece and Troy, it was possible to speak of the international spirit of the early Bronze Age and all this was really building up around 2500 BC, and then you could see that different things continued to develop in the middle Bronze Age so that by, shortly after 2000 BC in Crete, you had the Minoan palaces, the first Minoan palaces, which you can claim to be the origins of complex society or maybe even state society in Crete. And then by 1600 BC on the mainland of Greece, Mycenae, you have broadly similar things but it takes a little later to get going on the mainland. And so it was possible to think of these things while not denying that there were some points of contact with the Near East and with Egypt to say that those weren't necessarily terribly significant and it was endogenous processes, it was local - local working of endogenous rather than coming from outside, exogenous processes, which were at work and, clearly, the metallurgy was important. And then after the social system I talked about the evidence for trade, the trading subsystem, and we had lots of evidence there. It was the obsidian in the early days, the metallurgy in the early Bronze Age, but also lots of pottery forms, ceramic forms, indications of trade and probably also metal vessels which are not much preserved but you could see from some of the pottery forms the most characteristic form in the early Helladic II period and also in the Cyclades, then, it's a so-called sauceboat which looks a bit like a sauceboat, that's why it's called that, it was probably a drinking cup, but it's very elegant and just one or two exist in gold and it looks something that was started off in metal and then was copied in - in pottery, and also the famous Trojan two handled drinking cup, the so called depas amphkypellon, that existed in silver and you can see that it must have been a metal form that was then imitated in - in pottery. So you've got the trading system, then the other system that, or subsystem, that I tried to think about was what I call the symbolic and projective subsystem, that's rather a mouthful, but the development of religious belief as a projection and the development of symbolism, including the Cycladic figurines and so on, developments on the intellectual side, or as we would call it today the cognitive side, that all seemed to be related together. And so in writing that book, "The Emergence of Civilisation", I drew on an idea from economics, the so-called multiplier effect, and what seemed to be happening was that as one subsystem grew, as metallurgy developed, it had impacts in other subsystems. For instance, the availability of metal meant that you now had weapons, you had daggers. They soon lengthened to be swords, so you had a huge impact on military technology. Then also metal seemed to be the first form of serious valuables in the Aegean, silver and gold as well as bronze, so you had value systems developing which had a huge impact in the social subsystem. Then the development of technology allowing better ships because there's evidence in the Cycladic early Bronze Age for longboats with a lot of rowers powering them before the sail came into general use. So these things were working together and it was from the interactions among the subsystems that you found really serious transformations taking place that led first of all in Crete and then elsewhere to the emergence of complex society, or state society, or what's sometimes called civilisation.