What do "contradictions" mean in Buddhist philosophy?

You must have heard about the Four Noble Truths. There is dukkha, origination of dukkha, cessation of dukkha, and path or method of incrementally attaining said cessation of dukkha.

Dukkha is defined as "Association with the unbeloved; separation from the loved; Not getting what is wanted".

If you sit down and meditate on the above you should see that it means a kind of subjective discord or momentary mismatch between "what is" (what you see as reality") and "what should be" (your expectation or romantic ideal).

This is an essence of contradiction, a kind of inner conflict (in the stream of recognitions/associations/intepretations that creates an illusion called consciousness.)

All dukkha has a nature of contradiction, conflict, clash, discord, disharmony, falsity, wrongness, mismatch. Conversely, the opposite of dukkha has a nature of match, concord, harmony, peace, suchness, truth.

Next, the Second and Third Noble Truths define origination and cessation of dukkha as clinging/attachment and letting go correspondingly. This is a perfectly valid and correct observation in the subjective universe of an individual given our definition of dukkha as mismatch or contradiction between "is" and "should". Indeed, it is attachment to an unrealistic expectation that holds the contradiction together, and letting go of this expectation dissolves the contradiction.

However, many of the more coarse and brutal cases of inner conflicts and contradictions come from the objective situation surrounding the individual. For example, an external conflict with law caused by stealing creates an internal conflict between person's desire to take a walk and the reality of them being confined in prison. If you follow this chain further back, you'll see that the conflict with law was caused by a conflict between the person's desire to have the object and the reality of it belonging to its rightful owner.

This is just a basic contrived example, but you can see how conflicts and contradictions tend to chain. Similar examples can be described with other of the five precepts e.g. lying, sowing divisive speech, violence, and intoxication. They create a kind of contradiction that chains on and on until it becomes a painful experience of expectation mismatch in someone's mind.

This is why the Fourth Noble Truth, the path, does not just prescribe sitting in meditation and letting go of all attachments to achieve cessation of inner conflict, no. Buddha knew that such an approach would be completely unrealistic if the external situation keeps generating causes of coarse external contradictions becoming new internal contradictions becoming dukkha. This is why the Noble Eightfold Path describes a set of practices designed to reduce and eliminate all sources of coarse external contradictions. Only in its later "steps" does it talk about inner practices like mindfulness and meditation.

That said, the noble path as it's given in traditional literature is just a schematic. The idea of the path is clearly the methodical systematic elimination of causes of all conflict and contradiction, starting from the coarser and progressively more and more subtle.

Once we get to the jhana practice, the same principle holds. The first four jhanas are elimination of contradictions, from the more coarse ones in the first jhana (the thoughts that something is wrong with self or the world), to the more refined conflict of the second jhana (between the image of rightness created with the autosuggestions, and the fact that one has to keep using the autosuggestions to keep generating the rightness, which makes it somewhat artificial and inauthentic). The same idea plays out in the third and forth jhanas, and then in the four formless jhanas, but it would be irresponsible for me to try and explain it all in a single answer.

The important thing to understand is that this principle, of dukkha having the nature of contradiction and cessation of dukkha requiring cessation of contradiction, holds from the beginning of Buddhist path all the way to Nirvana.

What I'm doing here is trying to expound the meaning of the traditional Pali Canon descriptions, in my own words. In doing so, it is a bit difficult to come up with universally acceptable terminology so forgive me if my nouns and adjectives are all over the place. I hope the above gives a more clear idea of what I meant by the contradictions.