Engels postulated three laws of dialectics from his reading of Hegel's Science of Logic.[27] Engels elucidated these laws as the materialist dialectic in his work Dialectics of Nature:

The law of the unity and conflict of opposites
The law of the passage of quantitative changes into qualitative changes
The law of the negation of the negation
The first law, which originates with the ancient Ionian philosopher Heraclitus,[28] was seen by both Hegel and Vladimir Lenin as the central feature of a dialectical understanding of things:

It is in this dialectic as it is here understood, that is, in the grasping of oppositions in their unity, or of the positive in the negative, that speculative thought consists. It is the most important aspect of dialectic.

— Hegel, Science of Logic, § 69, (p. 56 in the Miller edition)
The splitting of a single whole and the cognition of its contradictory parts is the essence (one of the "essentials", one of the principal, if not the principal, characteristics or features) of dialectics. That is precisely how Hegel, too, puts the matter.

— Lenin's Collected Works Volume 38, p. 359: On the question of dialectics.
The second law Hegel took from Ancient Greek philosophers, notably the paradox of the heap, and explanation by Aristotle,[29] and it is equated with what scientists call phase transitions. It may be traced to the ancient Ionian philosophers, particularly Anaximenes[30] from whom Aristotle, Hegel, and Engels inherited the concept. For all these authors, one of the main illustrations is the phase transitions of water. There has also been an effort to apply this mechanism to social phenomena, whereby population increases result in changes in social structure. The law of the passage of quantitative changes into qualitative changes can also be applied to the process of social change and class conflict.[31]

The third law, "negation of the negation", originated with Hegel. Although Hegel coined the term "negation of the negation", it gained its fame from Marx's using it in Capital. There Marx wrote this: "The [death] knell of capitalist private property sounds. The expropriators [capitalists] are expropriated. The capitalist mode of appropriation, the result of the capitalist mode of production, produces capitalist private property. This is the first negation [antithesis] of individual private property. [The "first negation", or antithesis, negates the thesis, which in this instance is feudalism, the economic system that preceded capitalism.] ... But capitalist production begets, with the inexorability of a law of Nature, its own negation. It [final communism, the synthesis] is the negation of [the] negation."[32]