There are two ideas hidden in the word system: the idea of a system as a whole and the idea of a generating system.

1. A system as a whole is not an object but a way of looking at an object. It focuses on some holistic property which can only be understood as a product of interaction among parts.

2. A generating system is not a view of a single thing. It is a kit of parts, with rules about the way these parts may be combined.

Almost every ‘system as a whole’ is generated by a ‘generating system’. If we wish to make things which function as ‘wholes’ we shall have to invent generating systems to create them. In a properly functioning building, the building and the people in it together form a whole: a social, human whole. The building systems which have so far been created do not in this sense generate wholes at all.

There are two ideas hidden in the word system: the idea of a system as a whole and the idea of a generating system.

The word system, like any technical word borrowed from common use, has many meanings and is imprecise. This lack of precision in a technical word might seem dangerous at first; in fact it is often helpful. It allows new ideas to flourish while still vague, it allows connections between these ideas to be explored, and it allows the ideas to be extended, instead of having them cut short by premature definition and precision.

The word ‘system’ is just such a word. It still has many meanings hidden in it. Among these meanings there are two central ones: the idea of a system as a whole, and the idea of a generating system.

These two views, though superficially similar, are logically quite different. In the first case the word ‘system’ refers to a particular holistic view of a single thing. In the second case, the word ‘system’ does not refer to a single thing at all, but to a kit of parts and combinatory rules capable of generating many things.

A system as a whole is not an object but a way of looking at an object. It focuses on some holistic phenomenon which can only be understood as a product of interaction among parts.

Let us consider some examples of holistic phenomena which need to be viewed as systems.

The great depression is an obvious example of a holistic phenomenon. We cannot understand the depression, except as a result of interaction among rates of consumption, capital investment and savings: the interactions can be specified in the form of equations; if we follow these equations through to their conclusion, we see that under certain conditions they must always lead to a depression.

The stability of a candle flame is another example of a holistic phenomenon. Why does it maintain approximately the same size and shape throughout its flickering? In this case, the ‘parts’ are flows of vaporized wax, oxygen and burnt gases — the processes of combustion and diffusion give the interaction between these flows — and these interactions show us at what size and shape the flame will be approximately stable.

The strength of a rope is another example of a holistic property. This strength is a result of interaction among the individual strands, caused by the twisting of the rope: untwisted, the rope’s strength is governed by the weakest strand; twisted, the strands act together and increase their strength.

Another example of a holistic property is the relation between input and output in any computer. In the toy computer called ThinkADot, a ball dropped into one of three holes comes out on one of two sides. The output side is not determined by the input hole, but by the input hole and the internal state of the machine, which is itself determined by the sequence of past inputs. In order to understand this behavior, we must understand the machine as a whole, considering the past inputs and the internal states as parts, and the way that different sequences of inputs and internal states create specific new internal states and outputs as interactions.

Another kind of holistic behavior is that instability which occurs in objects that are very vulnerable to a change in one part: when one part changes, the other parts change also. We see this in the case of erosion: cutting down trees robs the soil of the roots which hold it together, so that wind and water can strip the soil of all remaining plants, and make a desert. We see it again in the death of the traditional farm: when the combine harvester replaced traditional harvesting, the entire balance of scale economies was destroyed, the little farms collapsed, and gave way to giant farms.

Let us summarize the content of these examples. In every case we are confronted with an object which displays some kind of behavior which can only be understood as a product of interaction among parts within the object. We call this kind of behavior, holistic behavior.

The central point of the whole argument can be stated very simply. The most important properties which anything can have are those properties that deal with its stability. It is stability which gives a thing its essential character. The strength of an arch, the even burning of a flame, the growth of an animal, the balance of a forest ecology, the steady flow of a river, the economic security of a nation, the sanity of a human individual, the health of a society: these are all, in one way or another, concerned with stability.

Stability, no matter in which of its many forms, is a holistic property. It can only be understood as a product of interaction among parts. The essential character of anything whatever, since it must at heart be based on some kind of stability, must be understood as a product of interactions within the whole. When we view a thing in such a way as to reveal its character in holistic terms, we speak of it as a system.

In order to speak of something as a system, we must be able to state clearly:

(1) the holistic behavior which we are focusing on;

(2) the parts within the thing, and the interactions among these parts, which cause the holistic behavior we have defined;

(3) the way in which this interaction, among these parts, causes the holistic behavior defined.

If we can do these three, it means we have an abstract working model of the holistic behavior in the thing. In this case, we may properly call the thing a system. If we cannot do these three, we have no model, and it is meaningless to call the thing a system. The idea of a system is synonymous with the idea of an abstract model of some specific holistic behavior. We may speak of the economic system in a country, because we can construct a system of equations which reproduce important holistic phenomena like depressions or inflation. If we couldn’t do this, it would be meaningless to speak of economic systems.

We must not use the word system, then, to refer to an object. A system is an abstraction. It is not a special kind of thing, but a special way of looking at a thing. It is a way of focusing attention on some particular holistic behavior in a thing, which can only be understood as a product of interaction among the parts. Everything under the sun may be viewed as a system: a man smoking a cigarette may be viewed as a system; so may a leaf drifting in the wind; so may a brick; so may mankind on earth. But it only becomes a system if we abstract from it some special holistic property, which we cannot explain except in terms of interactions within the whole. Without a specific statement of what holistic behavior we have in mind, what interactions among what parts cause this behavior, and how they do so, calling a thing a system is no more than saying: “This is a pretty complicated thing, and I don’t understand it very well”.

The idea that a system is an abstraction needs emphasis. Think of a flower as a system. If we want to understand the fact that the flower buds, and swells, and blooms — that we must certainly do by looking at the flower as a system. In this case it is the interaction among the parts which creates the behavior of the whole. But the same flower has other properties which are not helped at all by thinking of the flower as a system: if it is used as a projectile, then its trajectory cannot be explained as a result of interactions among its parts, and if it is given as a gift, there is nothing that the flower does, no matter how complex the situation, that needs to be understood as a result of interactions among the flower’s parts. The idea of a system is helpful only in understanding kinds of behavior which result from interactions among parts.

Furthermore, even though we call a thing a system when we try to view it as a whole, this does not mean that we ever really view the thing in its entirety.

When we look at an airline from a systems point of view, we may focus on its scheduling — and we shall learn that because the airline only has a limited number of aircraft, the schedule of a flight from New York to Chicago turns out to be dependent on the schedule of another flight from Minneapolis to Salt Lake City. In this instance, we are looking at the airline ‘as a whole’, because we are looking at the interactions among parts, but we are not concerned with the last button on the last mechanic’s cap. The notion of ‘whole’ refers only to the breadth of vision, not to the inclusion of detail: it is still abstract.

Most often common language obscures this very badly. When we speak of the solar system, or a hi-fi system, or an airline system or of a plumbing system, the words are used in such a way as to suggest that the ‘system’ is synonymous with the objects. But just occasionally the word is used correctly, even in common language. For instance, when we speak of the Ptolemaic system as opposed to the Copernican system, in each of the cases the word ‘system’ is used correctly: it refers to an abstract way of looking at the interaction among earth, planets, sun and stars — not to the objects themselves.

The discipline of abstraction has one drawback. Occasionally we are confronted with phenomena which are clearly the products of interactions — but the interactions are so complex that we cannot see them clearly, and we cannot make the effort of abstraction successfully. Take, for instance, the baffling complexity of a seagull landing, or of an ecstatic, screaming, laughing girl. In these cases a too rigid insistence on the idea that a system is an abstract model, might easily lead us to abstract out some facile inessential system — at the cost of the wonder which is really there.

This is exactly what happens when a systems analyst looks at a building: he/she manages to describe the circulation, the acoustics, the heating and the load-bearing structure as systems — and fails to identify the most interesting human and social systems, because he/she can’t describe them in explicit terms.

Thus, there is a second lesson to be learned. The first lesson said: don’t call a thing a system unless you can identify the abstract system you are talking about. The second lesson says: learn the first lesson, but don’t let it railroad you into making facile abstractions.

When we are confronted with a complex thing, we often begin with nothing more than a feeling or a ‘sense’ that it functions as a system. Driven by this feeling, we then try, painstakingly, to abstract out just that holistic behavior which seems essential, and those interactions which cause the behavior. This is an active process. It begins with feeling, and sensing, and only turns to thinking later. Start with some aspect of life so interwoven that you feel in your bones it must be a system, only you can’t state it yet — and then, once you can feel it clearly, try to pin the system down, by defining the holistic behavior you are discussing and which interactions among which parts create it. But feel it clearly first, before you try to think it.

The systems point of view is not neutral. It will change your whole view of the world. It will lead you to realize that the most important characteristics of human individuals are products of their interactions with other people. It will lead you to realize that the life of nations — though these nations may seem self-sufficient — is produced by interactions in the whole world, and that they only get their strength from their position in this larger whole. It will lead you to see that the health of cities is produced by interactions among interdependent parts, including houses, cafés and theatres, yes, but also equally including slums and graveyards.

The system viewpoint is a modern, disciplined, version of the sense of wonder. It is that view of things which man takes when he becomes aware of oneness and wholeness in the world.

A generating system is not a view of a single thing. It is a kit of parts, with rules about the way these parts may be combined.

This is a different use of the word system from the first one. In colloquial English we often use the word system to mean ‘a way to do something’: that’s what a betting system is; that’s what the Montessori system is; that’s what the democratic system is.

Each of these systems is, at heart, a system of rules. A betting system tells you how to place your bets, the Montessori system lays down rules to be followed by children and teachers in nursery school, the democratic system of government lays down certain rules about the nature of representation, the choice of representatives and the conduct of elections. In all these cases, the rules are designed to generate things. A betting system supposedly generates winning bets, an educational system generates well-educated pupils, the democratic system supposedly generates freedom and good government.

We may generalize the notion of a generative system. Such a system will usually consist of a kit of parts (or elements) together with rules for combining them to form allowable ‘things’. The formal systems of mathematics are systems in this sense. The parts are numbers, variables, and signs like + and =. The rules specify ways of combining these parts to form expressions, ways of forming expressions from other expressions, ways of forming true sentences from expressions, and ways of forming true sentences from other true sentences. The combinations of parts, generated by such a system, are the true sentences, hence theorems, of mathematics. Any combination of parts which is not formed according to the rules is either meaningless or false.

A generating system, in this sense, may have a very simple kit of parts, and very simple rules. Thus the system of triangles which may be put together to form a square, is a generating system. Its rules generate all the ways of putting these triangles together to form a square. It is typical of a system that the rules rule out many combinations of the parts. Thus these triangles could be put together in an infinite variety of ways — but most of these ways are ruled out, because the outside perimeter is not a square and this thing is not connected.

Another example of a generating system is the system of language. Here we have rules at several different levels. At one level, the letters are the parts, and there are rules which govern the way that letters may be put together to form words. In English there could be no word beginning with Rx. The rules of phonology prohibit it. At another level, the words are themselves parts, and there are rules which govern the kinds of sentences which may be made from words.

Perhaps the most interesting and important generating system in the world is the genetic system. Every animal in the animal kingdom is generated by a set of chromosomes specific to that animal. Each chromosome in turn is generated by four bases (like a necklace which uses only four kinds of bead). The four bases form a kit of parts which generates the chromosome. These chromosomes themselves provide the rules for building amino acids (another kit of parts), proteins from amino acids (another kit of parts), cells from proteins (another kit of parts) and then build the animal from cells. The kit of parts formed by the four bases, and their rules of combination, indirectly generates every animal there is.

A building system is a generating system in this sense. It provides a kit of parts — columns, beams, panels, windows, doors — which must be put together according to certain rules.

Almost every ‘system as a whole’ is generated by a generating system. If we wish to make things which function as ‘wholes’ we shall have to invent generating systems to create them.

There is a relationship between the two ideas of system which have been defined. Almost every object with behavior that depends on some ‘system as a whole’ within the object, is itself created by a generating system.

Take an obvious and simple case: a hi-fi system. Its purity of performance can only be understood as a product of the combined effect of all the various components, working as a whole. The same hi-fi system is also generated by a generating system: the kit of all the parts on the market, and the rules governing the electrical connections and impedance matching between these parts.

To take a more complicated case: the railroad switch-yard. It plainly functions as a whole. In order to understand it as a device for breaking up and making trains, we must focus on the sequence of switches, and on the fact that the length of track in front of the switches depends on the length of track behind the switches and on the length of trains. At the same time, the switch-yard is also plainly generated by a generating system. The pieces of track, switches, couplings, cars, together with the rules for putting them together, form a kit of parts which generates properly functioning switch-yards.

The most complicated case of all, and the clearest, is that of an animal. A landing seagull certainly needs to be seen as a system: so does almost everything else that seagulls do. At the same time, this seagull is created by a generating system: the genetic system. An animal is both something which needs to be seen holistically, and generated by a generating system.

The relationship between holistic systems and generating systems is easy to understand. If an object has some holistic property caused by interaction among parts — then it is clear that these particular parts and these particular interactions will only come into being if the parts have very constrained relationships to one another. The object then, must be generated by some process which assembles parts according to certain constraints, chosen to ensure the proper interaction of these parts, when the system operates. This is exactly what a generating system is.

The generating system need not be conscious (as in the case of the switch-yard), nor even always explicit (as in the genetic case). Sometimes the processes which make up the generating systems are integral with the object being formed — thus the candle flame is generated by chemical processes which are the same as those processes which then maintain the system’s equilibrium and make up the interacting parts, when we view the flame as a holistic system.

It is true then, that almost every ‘system as a whole’ is generated by a generating system. This axiom contains a remarkable lesson for designers. Man as a designer is concerned with the design and construction of objects which function as wholes. Most of the important properties a city needs to support life, for instance, are holistic properties.

Our axiom means this: to ensure the holistic system properties of buildings and cities, we must invent generating systems, whose parts and rules will create the necessary holistic system properties of their own accord.

This is a radical step in the conception of design. Most designers today think of themselves as the designers of objects. If we follow the argument presented here, we reach a very different conclusion. To make objects with complex holistic properties, it is necessary to invent generating systems which will generate objects with the required holistic properties. The designer becomes a designer of generating systems — each capable of generating many objects — rather than a designer of individual objects.

A final word of caution. As we have already seen, a building system is an example of a generating system. It is a kit of parts with rules of combination. But not every generating system necessarily creates objects with valuable holistic properties. The generating system which makes squares out of triangles is an example. It is a perfectly good generating system; yet the objects it produces do nothing: they have no holistic system properties whatever. In the same sense, those building systems which have so far been conceived make buildings, but they do not make buildings with any really important holistic system properties. In a properly functioning building, the building and the people in it together form a whole: a social, human whole. The building systems which have so far been created do not in this sense generate wholes at all. While it is inherent in the generating system of an animal that the finished animal will work as a whole, it is not inherent in any of today’s building systems that the buildings they produce will work as social or human wholes. Creating building systems in the present sense is not enough. We need a new, more subtle kind of building system, which doesn’t merely generate buildings, but generates buildings guaranteed to function as holistic systems in the social, human sense.