One is not thereby a learned man merely because one speaks much. He who is secure, without hate, and fearless is called learned.

-- Buddha

The perception of the external world is dependent on the mind. We cannot find a material world that exists totally separately from the mind. The material world is a reflection of the mind rather than an independently existing thing. If your understanding of this leads you to realise the nature of mind, you will automatically realise the nature of the external world. It is not necessary to separately examine the nature of the world. We realise the nature of the external world through realising the nature of mind because of unity in diversity. This is the same as the realisation of non-dual wisdom.

-- Gampopa

The Karmapa gave another example illustrating how important and necessary all traditions of Buddhism are. Imagine, he said, a large copper vat filled with milk. It takes four people to lift up, using their strength equally so that the milk does not spill out. There may be some little difference between the four people but basically they are the same. Nevertheless, the Karmapa explained, if one of the four could not carry their side, the milk would spill out. And it would go out even faster if one of the four thought they could do the lifting on their own. So the four need to cooperate in the project of lifting the vessel, which the Karmapa explained as an analogy for the Buddha’s teachings being carried by different traditions. If one side tried to carry the entire vat and spilled the milk, the whole of Buddhism would be diminished; if even one of the other schools disappear, it means that Buddhism is disappearing, so everyone needs to work together. In sum, he said that if the teachings, which are the antidote for our afflictions, become the cause for afflictions to increase, we are finished, so we should consider this carefully.

~Karmapa: Cultivating the Delight of Rejoicing and the Freedom from Prejudice

http://the17thkarmapa.blogspot.sg/2016/02/cultivating-delight-of-rejoicing-and.html

There are three kinds of dharma practitioners: firstly, there are those who look like practitioners outwardly, but inwardly they are not real practitioners; secondly, there are those who talk very high, but have no realisation at all; thirdly there are those who do not look like practitioners outwardly, but who are in fact genuine practitioners inside.

-- His Holiness Chatral Sangye Dorje Rinpoche