I am well aware that the very idea of using methods of theoretical physics, especially quantum mechanics, for describing economic phenomena must cause a healthy dose of skepticism from the physicists. Therefore, I emphasize that the discussion deals with the fact that only the mathematic framework of theoretical models of the respective physical systems are transferred to the physical economic models.

I incorporate into economics only the formal structural aspects of physical theories. First of all are the equations of motion for the many-particle systems, which just by themselves must not be too rigidly attached to real physical microscopic objects. Equations – they are just equations and nothing more, and if they are a beneficial descriptive tool in another science, why not make use of them? I repeat that this is just a useful mathematical object which can and should be used as a theoretical tool where it can provide benefit. For instance, in quantum mechanics wave functions and the Schrödinger equations have been successfully used for the incorporation of the uncertainty and probability principle into physics. Why, then, can we not then apply the same mathematical apparatus to the analogous uncertainty and probability principle in economic theory for purposes of mathematical description?

It is obvious that this is only an initial approximation to reality. But we are talking about modeling economic systems, and models are only models, giving only an approximate shape to the object being modeled. My physical models of economic systems also do not pretend that they are complete and precise; they can give only the approximate patterns of our market economic world, only the specific stage in our understanding of the real economic world transposed into the language of mathematics. A physical economic model is nothing other than a certain ideal, imagined construction, aimed at explaining one or more aspects of the studied phenomenon. The question is not whether it is correct or not, but whether it is useful in helping to reach a true understanding of the real economic world. Nothing more. I think that by means of this approach, some insight into the important market economy phenomena has been gained in this study.

Ten years ago I published the small book “Physical Modeling of Economic Systems: The Classical and Quantum Economies” [4]. It was my first attempt to develop an economic theory ab initio, and constructed an axiomatic basis of the theory from a limited set of first principles. The basic hallmarks of the theory that made it probabilistic and quantitative are as follows.

First. A careful, step-by-step development of the market agent-based physical economic models, where market agents play a main role in market phenomena.

Second. The complete integration of uncertainty and probability perspectives throughout the theory.

Third. A unifying, analytic framework that uses equations of motion in the formal price economic space to describe economy evolution in time.

For the last ten years, I have continually strived to advance the theory and to make it more clear and justified. In particular, for this purpose I developed the special mathematical apparatus, which is referred to in the book as probability economics. Still, I considerably advanced the theory by means of taking into consideration quantities of market goods as independent variables along with their prices. Due to this innovation, the economic price space was expanded up to the economic price-quantity space. During this time I also developed mathematical apparatus for describing the many-good, many-agent market economies. Despite the fact that achievements and expansions of theory mentioned above are very substantial, my new book carries the title “Probabilistic Economic Theory” and is, in essence, the second extended edition of my first book, in which I presented only very beginnings of the method of the agent-based physical modeling of economic systems and the basics of probabilistic economic theory.

In this book, the fundamental concepts of economic theory are exposed to critical rethinking for the purpose of answering such eternal questions of economic theory such as those regarding supply and demand, as well as market price and market force, market process and market equilibrium, invisible hand of market etc. I look at how all these concepts should be incorporated into economic theory and conveyed quantitatively in the same language in which physicists, chemists and other professionals in the so-called natural sciences present their theories, i.e., in the language of mathematics. In the book I presented maximally simplified models, in which only the most important special features and details of work of markets are described by means of maximally simplified mathematical apparatus. Let us stress here that the main aim of such basic models is only to reveal the essence of the studied phenomenon, not more. After this is accomplished, we can then develop the models further, including other, more sophisticated effects within them. This is the only true way of modeling science. Therefore, Chapters I–VIII are easily understood by first-year economics students. But the subsequent Chapters IX and X require an existing, thorough knowledge of physics, somewhere around the level of upper year physics courses. They only need have the slightest grasp of economic phenomena and laws of human action in the market economy, obtained, for example, in the course of reading the first chapters of this book. Generally, this book can be considered as an introduction into economics, written for physicists in standard physics terminology. The book, by the way, was initially taught as a set of lectures on economics for physics department students. If, after reading this book, a physics student has the impression that the presented physical economic models are quite simple and understandable, then I have solved a personal challenge. Indeed, I feel that the more complex the studied systems are and the phenomena within them, the simpler the model must be, taking into consideration only those effects which are of prime importance for describing the studied phenomena.

The book, as noted above, is the collection of lectures, each of which is called to answer one or several questions given above. The genre of lecture (or essay) is selected for the purpose of concentrating on the compact, clear presentation of physical economics. In it I have used a whole series of new ideas, concepts and notions for the economic theory, which arise from theoretical physics. I believe I have succeeded in avoiding the necessity of making numerous surveys and references, the like of which can be found in most other textbooks on economics and economic history. Therefore, references in the book are made only to those sources which were actually used for the fulfillment of studies, the development of models, and writing of the book. To provide convenience to students in lectures, figures and fragments of the text are reproduced several times in some chapters.

It should be emphasized once more that I borrowed ideas, concepts and notions from physics, many of which are completely consistent with the discoveries of the classical economic theories of the 19th century, the first of which being the subjective theory of value. This concerns first and foremost such important milestones in the development of classical economic theory as [5]:

1. Regularity in the sequence of market economic phenomena.

2. Exclusive and dominant roles of market agents in the market phenomena.

3. Uncertainty of the future and the probabilistic nature of all market agents’ decisions.

4. Social cooperation of market agents etc.

All these aspects of human economic activities have an exceptionally important effect on market processes and determine the course of economic development. But any formal methods of providing an adequate formal description of these economic phenomena and processes at a strict mathematical level in economic theory, until now, have been absent. Necessity and expediency of borrowing by economics from physics is substantiated by the fact that theoretical physics already developed sophisticated mathematical methods to incorporate analogous concepts into formal physical models. The method of equations of motion was first, and uses systems of differential equations of the 1st and 2nd orders, but economic theory still did not.

I would like to stress here that this creative process of the transfer of the formal methods of physics into classical economic theory presents the main point of the concept of the agent-based physical modeling of the economic systems and physical economics as a whole. One can say that, in essence, physical economics is first and foremost the mathematical apparatus of classical economic theory at the contemporary level of its development. This mathematical apparatus is borrowed from theoretical physics and has therefore practically nothing to do with the mathematical apparatus of neoclassical economics.

In order not to overload the text of the book by the descriptions of the known concepts of classical economic theory upon which I rested in this investigation, I make use of complete quotations from the fundamental monograph of Ludwig von Mises [5] as epigraphs to each part and chapter of the book, with two exceptions. This method allowed me to avoid the mixing of completely different styles of the presentation in the book, which could hinder the perception of the text by readers. This is very important for me, since I have attempted to not to disappoint the readers, and to convince them of how it is fruitful to make use of achievements in theoretical physics for the development of economics. The point is not in the book’s detail, but rather in its broader concept of agent-based physical modeling of economic systems, which, in my view, has enormous potential. Here lies, I think, a new and enormous field for investigation, in which an abundant harvest will be gathered for many decades yet to come. I hope that the readers will obtain a certain benefit from the acquaintance with this new physical economic perspective for economic theory.