The question of change (and what determines it) is a fundamental part of philosophy. In spite of appearances, nothing can remain the same – all life is development, or motion, and all development involves a series of changes. When we consider things in their motion, change and interconnection, we are at once confronted with contradiction.
Every phenomenon in nature contains contradictions, opposites which exist together in unity. Development comes about through the struggle and unity of these opposites. Contradiction is an internal process and the basis of all quantitative development.
For example, cause and effect make up a unity of opposites. Or, bourgeoisie and proletariat together make up capitalist society, also as a unity of opposites. The two opposite elements of a contradiction are both mutually exclusive and mutually dependent. Their unity and struggle is absolute, quantitative and ongoing.
All processes develop in stages. Development occurs from the division of a unity into mutually exclusive opposites and their reciprocal relation. The relationship between the two sides of a contradiction becomes more contradictory within each stage, forcing the emergence of a new quantitative stage. Quantitative, stepwise, change creates the conditions for qualitative changes to occur. For instance, heat applied to cold water in a kettle causes the water to change, becoming hotter and hotter – a quantitative change – until the water boils and turns into something new, steam – a qualitative change.
Antagonism replaces and destroys contradiction: it is the mode of destruction and transformation to a new quality. For instance, in Russia in 1917, the antagonism between classes boiled over into revolution in which the working class and peasantry took power, thus creating a new kind of society. So out of this process, a synthesis, a new quality, a new unity of opposites, is born. A new process emerges to replace the old. All qualitative changes occur as leaps. They can appear to come from nowhere, but in fact are a result of the old contradictions becoming impossible to reconcile.
In contrast, religion attributes the changes going on in the world to god, whilst metaphysics sees nature as an arbitrary collection of objects and events, independent of and isolated from one another. Metaphysics wrongly asserts the cause of change as being not inside things but outside them. Dialectics grasps that internal contradiction is in all things and is the basis of quantitative and qualitative development. To understand the development of a thing, we must study it internally and in its relations with other things.
Changes in society are due chiefly to the development of the internal contradictions in society, that is, the contradiction between the productive forces and the relations of production, the contradiction between classes. The development of contradictions pushes society forward.