国家的统一，人民的团结，国内各民族的团结，这是我们的事业必定要胜利的基本保证。但是，这并不是说在我们的社会里已经没有任何的矛盾了。没有矛盾的想法是不符合客观实际的天真的想法。在我们的面前有两类社会矛盾，这就是敌我之间的矛盾和人民内部的矛盾。这是性质完全不同的两类矛盾。 - Mao Zedong

Medical education should be reformed. There’s no need to read so many books. How many years did Hua Tuo spend at college? How many years’ education did Li Shizhen of the Ming dynasty receive? In medical education there is no need to accept only higher middle school graduates or lower middle school graduates. It will be enough to give three years to graduates from higher primary schools. They would then study and raise their standards, mainly through practice. If this kind of doctor is sent down to the countryside, even if they haven’t much talent, they would be better than quacks and witch doctors and the villages would be better able to afford to keep them. The more books one reads, the more stupid one gets. The methods of medical examination and treatment used by hospitals nowadays are not at all appropriate for the countryside, and the way doctors are trained is only for the benefit of the cities. And yet in China over 500 million of our population are peasants.

If a man wants to succeed in his work, that is, to achieve the anticipated results, he must bring his ideas into correspondence with the laws of the objective external world; if they do not correspond, he will fail in his practice. After he fails, he draws his lessons, corrects his ideas to make them correspond to the laws of the external world, and can thus turn failure into success; this is what is meant by "failure is the mother of success" and "a fall into the pit, a gain in your wit".

和形而上学的宇宙观相反，唯物辩证法的宇宙观主张从事物的内部、从一事物对他事物的关系去研究事物的发展，即把事物的发展看做是事物内部的必然的自己的运动，而每一事物的运动都和它的周围其它事物互相联系着和互相影响着。事物发展的根本原因，不是在事物的外部而是在事物的内部，在于事物内部的矛盾性。任何事物内部都有这种矛盾性，因此引起了事物的运动和发展。事物内部的这种矛盾性是事物发展的根本原因，一事物和他事物的互相联系和互相影响则是事物发展的第二位的原因。这样，唯物辩证法就有力地反对了形而上学的机械唯物论和庸俗进化论的外因论或被动论。这是清楚的，单纯的外部原因只能引起事物的机械的运动，即范围的大小，数量的增减，不能说明事物何以有性质上的千差万别及其互相变化。