Contradiction is the inability of a complex system to internalize new data and new conditions

For example the labor vs employer conflict and capital expansion vs the natural world are the two biggest contradictions inherent to capitalism

Liberals maintain that the acquisition of new data can somehow offset the new conditions and resolve the contradiction, always, no more matter what, like magic

While materialists argue the system can't internalize data that contradicts the interests and incentives that animate the system entire (because that would negate the point of the system), which is Capital Accumulation

Basically if any new data that offsets capital accumulation is introduced to a system that is fueled by capital accumulation, far from what the liberals claim the contradiction is not resolved, it's in fact heightened

To understand and spot contradictions you have to understand the nature of the specific system at play and what primary mechanism animates it. For capitalism that is profitability, everything in the system revolves like planets around that dark bronze heart

So contradictions and the orientation of the system can be spotted when you see something that either services profitability or opposes/limits it

The text On Contradiction should be helpful. In addition, On Practice (first) and On the correct handling of contradictions among the people. Contradictions are basically things that are in conflict or opposites. The metaphysical philosophy of liberalism cannot comprehend contradictions existing within something, whereas dialectics see contradictions as inherent to all things.