The example that helped things start to click for me was the relationship between poverty and charity. At first glance they feel like opposites, poverty is a lack in essential needs, charity is an concentration of those essentials, distributed to those without.

But once you think about it some more, the only reason there is poverty is because some people have hoarded enough resources that they can dole them out as charity. Charity can only exist if poverty does, and poverty can only exist if the conditions for charity exist. Each contains the seed of the other within it, and they push and pull on each other. The more poverty there is, the more need for charity there is. The more charity exists, the more poverty that there must be. This is a dialectical relationship.