Final answer:
The concept in question is entropy, which is related to Physics, specifically within the realm of Thermodynamics. It explains why systems move from order to disorder without an input of energy. High entropy indicates a state of disorder which is naturally favored in isolated systems.
Step-by-step explanation:
The phrase “every system left to its own devices tends to move from order to disorder” refers to a fundamental concept in physics called entropy. Entropy measures the randomness or disorder within a physical system. The Second Law of Thermodynamics states that the entropy of an isolated system will tend to increase over time, meaning that systems naturally progress towards a state of higher disorder. This is exemplified in everyday life when objects like marbles tend to spread out once dropped, or a bedroom becomes messy without continuous maintenance. In terms of chemical and physical processes, entropy increases as molecules spread out from a concentration and as chemical reactions approach equilibrium.
Moreover, entropy is a measure of the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder. Since there are typically more disordered arrangements than ordered ones, disorder is more probable. For a decrease in entropy, or an increase in order, energy must be invested into the system. Without this input of energy, structures degrade, molecules disperse, and randomness prevails.