Fundamental Principles of Intellectual Humility

1. We are fallible.
Our reasoning powers, perceptions, and intuitions are limited. Sometimes they can mislead us without our knowing. Never presume to be infallible at any point.

2. There is always more to know.
We do not know how many possibilities, interpretations, or facts exist which may be relevant to our opinion. To claim we “know enough” would require that we know everything. Never presume to know enough.

Conclusion
There is always room for error. We would be wise to refrain from claiming certainty, or near certainty, about the world at any point.

If we can critically evaluate our beliefs and approach disagreements with these principles in mind, I think we'll be in a much better position to listen, learn, and dialogue, rather than accuse, criticize and preach. Acknowledging our fallibility mitigates our presumptuousness and arrogance, making it possible to respect our opponents and hear what they have to say.

While there's nothing wrong with holding opinions and propagating them with a degree of confidence, I think it's wise to resist speaking in terms of fact, rather than in terms of perspective. Many times, things are more complicated than they appear and we'll never know it until we do.