All real systems share a basic set of constraints that may be called universal and these serve as limiting factors in the articulation and phenomenal patterning of any system. A real system is any natural or human made system that occurs in objective reality, as opposed to non-real systems (i.e., abstract, conceptual or imaginary systems that lack any demonstrable basis in reality.) Non-real systems may be considered to be systems that are possible but as yet undemonstrated through experience. There is thus an overlap between real and non-real systems, and it is in this overlap that parallax and play exists for the emergence of new systems heretofore unrealized.

The universal constraints of real systems primarily involve energy exchange relationships upon a physical level. This energy exchange, of whatever kind of system, involves both inputs of one form of energy into a system complex, transformation of this energy along different pathways, and output of energy in one or more alternate forms, part of which is always the expenditure of heat. This thermodynamic model of energy exchange is really only part of the larger equation of energy transfer in real systems. It seems, all real systems are also subject to the constraints of gravity and gravitational energy, and these kind of constraints are not exactly thermodynamic by the conventional model. It is apparent also that other kinds of energy exchange transactions may be occurring in all real systems, albeit upon levels or in ways we have very little direct access to, observationally speaking, and at which we have not yet begun to understand what is really happening.

All real systems also contain, by virtue of their non-random organization of relationships, implicit information that is intrinsic to this relational patterning. Because an informational model is almost completely describable in terms of an thermodynamic analogy, many of the constraints that apply in the process of energy exchange transactions in system also apply to the informational carrying capacity of systems. We may venture the hypothesis in fact that all energy exchange events in the universe carry some kind of informational pattern in the structure of the event that is non-random. If this is true, we may further deduce that what is most characteristic of any system is its energy transactions, and all energy transactions in physical reality can be said to be relatively "systematic" in their occurrence. We know this for two sets of reasons. In the attempt to understand any energy transaction, we can always assume that there is always a net energy balance of zero in any equation we come up with, and this exact balance of inputs-to-outputs in any "energy" system is also directly analogous to a model of pure mathematical abstraction. At this point, pure energy transactions and naturally organized informational systems are directly correspondent with purely abstract mathematical models based upon logical equations. Of course, the complexity and chaos of underdetermined natural systems is virtually impossible to replicate by means of mathematical models, but the possibility for doing so is what drives the advance of supercomputing digital simulations of complex natural event structures like wave action or tornados.

What does all this mean? If we put aside the symbolic rhetoric of our own language and conceptual/ideological systems, and we approach any real system in its most basic terms, we can always find an exact mathematical model, however complex and relatively unavailable, that perfectly describes the deterministic behavior of the system in question in terms of its energy transactions. However chaotic and disordered an explosion might be, if we could replay the events in an exact sequence and simultaneously, we would be able to mathematically map the chain of energy reactions that composed such an event.

Some kinds of constraints are obviously connected to the energy transactions of systems--there is always a loss of heat energy in any real system, such that the efficiency of energy input to the used energy output is always less than 100%. And such a system can never be completely ordered in a non-random, deterministic sense, but its pattern will always contain some degree of random "noise" that is essentially unpredictable.

There are other related limitations we may find universal to all real systems. All real systems contain some degree of indeterminacy or variability built into it on a structural level. All real systems are subject to change and dynamic fluctuation over the long term. All real systems change along pathways that are paradigmatically predefined for systems of a similar kind and magnitude. Change in systems is inevitable. All real systems may be said to have a finite state-path trajectory that describes the life-cycle of a particular kind of system. The informational patterning associated with any real system is transformed on the basis of the stage of the life-cycle and the surrounding environmental events that occur to that system. 

All real systems achieve some stable, steady-state configuration in an intermediate phase of its development, which state configuration generally defines the system as such taxonomically and categorically. The mature or parent state of a normal system contains the general informational patterning that can be used in the classification and analysis of different kinds of systems. The fact of inexorable change of any real system imposes certain temporal constraints upon that system. Any system can last only so long before it perishes as such and its elementary components become recycled back into that huge physical cauldron of the universe. 

All systems, as systems, also have spatial constraints that limit their articulation. Real systems are not only bound in time, but in space as well. The reasons for the spatial constraint of systems are not so obvious as they might first appear to be. The best explanation I can make, and this is only hypothetical and tentative, is that in fact, in nature, we cannot have an infinite amount of energy in one place at one time, though we may have an extraordinary amount of energy thus concentrated in a finite area. Another way of looking at this problem, I believe, is to restate the idea that we cannot completely or clearly separate spatial dimensions from temporal event structures, and when we have the notion of space, we must include in the formula the problem of time. Hence, if anything is temporally limited due to change, that thing must also of necessity be spatially limited as well. The idea that any given spatial area, over a limited period of time, may contain only so much energy, and hence, information that is inherent to that energy patterning, sets limits as to the possibilities of growth and size of systems. 

Also, the idea that systems that depend upon energy transactions between an internal and external environment that are fundamentally different from one another, across some kind of  threshold, also entails that any real system can be only of finite 3 dimensional size. An infinitely large system could have no external environment with which to exchange energy. All energy would be contained within itself. I think another way of looking at this problem might be to state a precept like "an infinite amount of energy cannot be obtained from an infinitely small point in space-time." We cannot compress or squeeze all the energy of the universe into a single infinitesimally small "quantum" of space-time. We know that there are relativistic considerations increasingly at the lower known limits of size--there appears for instance to be increasing indeterminancy, intrinsic indeterminancy, of event structure on a small enough scale of measurement. I do not think the implications of this are completely understood, but it seems to me even "energy" as we understand this may be something completely different once we get to a small enough level of analysis.

Perhaps a simpler way of stating this is that all energy transaction events, and the systems they represent, occur in finite space as well as finite time, and thus require both limited space and time for their occurrence. 

We must ask, beyond space-time considerations of energy systems, what other constraints might all real systems share in common?

All real systems appear to maintain an indefinite internal state of dynamic equilibrium that is characterized by a gradient between a larger degree of energy contained internally within the system and the measure of energy outside of the system, which gradient is maintained and mediated by certain mechanisms, specific to each kind of system, that can maintain this gradient by transporting into the system greater quantities of energy per unit time and space than are lost from the system either by work, organization or entropy in the system. This state of equilibrium in a system may be maintained in a stable manner such that it will not be drastically affected by minor perturbations or fluctuations of energy levels or exchanges between internal and external environments.

As a function of the complex internalized organization of systems in a non-random, semi-deterministic manner, it may be said that any system exhibits in its patterning certain synergistic properties that are emergent from the behavior of the system as a system, and that cannot be attributed completely to any single components or set of components of the system. In fact, so much does this appear to be the case that all of nature, and all of reality, appears to have organized and stratified itself on the basis of emergent properties, that, upon finer analysis, simply disappear as a consequence of the disruption of the system that produces the property in the first place. This is as true of protons and electrons in an atom of hydrogen or a molecule of water, as it is in an multi-cellular organism or in a star.

We end up with a paradox of systems in a sense being built of a house of cards, or rather, systems composed of other systems, in turn composed by other systems, based on properties attributed only holistically to systems and never to the component parts of those systems. There is little beyond the enormous intricacies and beauty of natural systems that is more remarkable than how emergent properties attributed to systems integration at one level, becomes the basis for the construction of higher-order systems, and how, in such a way, nature seemingly has constructed itself, in all its intricacies, from apparently almost nothing, to what we know it as, including ourselves in that world.

I would not say that these are the only features that are universal to all real systems. They all share complex relationships between constituent components, and they all occur within an environmental context that is essential to the stability and continuation of similar kinds of systems. Systems cannot arise in environmental contexts that are not conducive to their occurrence and stability. While this may sound like a functional tautology, it is quite true that all systems are environmentally dependent upon the conditions that are conducive to their development as systems of a particular kind.

While it may seem self-evident to claim these kinds of features as basic to all real systems, less evident is the degree to which these same features may be used to describe, for instance, the functioning of human systems at the several levels that human systems articulate and in the contexts in which these systems have arisen and developed. Without the correct environmental conditions occurring, it is like that human systems, as cultural symbolic systems built upon the linguistic exchange and transmission of symbolic information, would have arisen in the way that they did, if at all. And we should pay heed ultimately to the same sets of constraints that drive our global civilization today, the insatiable demand for energy and the capacity to utilize this energy in effective ways.

General Systems Essays, Vol. II