# Structural and Symbolic Information in the Context of the General Theory of Information
## 1 Introduction  
Everything has its structure, and according to the contemporary approach in methodology of science, scientists discover structure, rather than the essence and nature of the studied phenomena (cf., for example, [1; 2; 3]). As a result of their research, scientists gain and publish information obtained from the structure under investigation. For instance, astronomers, such as [PERSON] and [PERSON], watched the changing positions of visible stars and, eventually, in 1627, published related tables with the numbers that described the structure of our planetary system. Extracted structural information was symbolically described by numbers making possible the discovery of dynamic regularities of the solar system made by [PERSON]. Formulated in terms of mathematical symbols, [PERSON]'s laws permitted, for example, successful predictions of the solar transits of Mercury in 1631 and of Venus in 1639, and eventually the launch of satellites and space probes. To achieve better understanding of information processes, it is useful to study relations between _structural_ and _symbolic information_[4; 5; 6; 7; 8], or, synonymously, between _bounded_ and _free information_[9], respectively. Symbolic information relies on a convention between the transmitter and receiver. In contrast to this, intrinsic structural information, on the contrary, is not based on conventions. For instance, when astronomers watch the changing brightness of distant stars, they receive structuralinformation about possible planets of those suns. At the same time, when sailors at night watch the changing brightness of a distant lighthouse at the shore, they receive both structural and symbolic information in the form of the optical code as a unique identifier of the beacon. It is possible to attribute structural information to all physical processes and systems. It may be often quantified in terms of physical entropy [5; 8; 10; 11; 12]. Physical structures, such as moving planets and their shining light, exist independently of life. On the other hand, the prediction of future events, such as solar transits, derived from observations made in the past, is a typical characteristic of life and, in particular, of humans. In order to facilitate future survival, genetic information also acts this way, as \"genomes do not predict the future but recall the past: they reflect the exigencies of history\" [13]. Information constitutes a bridge between lifeless physics and living beings struggling for survival. It is obtained by \"measurement in which a rate-dependent dynamical state is coded into quiescent symbols\" [14], and created by trial and error in the course of Darwinian evolution. The emergence of symbolic information may \"distinguish the living from the lifeless\", as the problem was raised already by [PERSON] ([15], p. 341). In this context, symbolic information has a purpose, while structural information does not. \"Evolution is based on function and--what is really new in physics--the 'purposefulness' of the function involved\" [16]. In many cases, portions of symbolic information may be true or false. A lighthouse on the shore, as the transmitter of information, may send a wrong code either as a result of a technical failure or intentional deception by the operators on land. Additionally, the sailor, as the receiver of information, may fail in properly reading or interpreting the code. In the case of structural information, however, if an alien astronomer observes the 11-year brightness cycle of our sun, he may falsely conclude that there is a big planet with an 11-year orbital period, similar to Jupiter. In that case, information extracted by the scientist from the measured signal may be false, but one may not reasonably blame the changing sunlight itself to be wrong, as in the case of the lighthouse code. There may also be \"fuzzy\" cases of unclear right or wrong, such as \"Tabby's star\", where the physical structure causing the received light signal remains elusive [17].