Marxists should not be afraid of criticism from any quarter. Quite the contrary, they need to temper and develop themselves and win new positions in the teeth of criticism and in the storm and stress of struggle. Fighting against wrong ideas is like being vaccinated -- a man develops greater immunity from disease as a result of vaccination. Plants raised in hothouses are unlikely to be hardy. Carrying out the policy of letting a hundred flowers blossom and a hundred schools of thought contend will not weaken, but strengthen, the leading position of Marxism in the ideological field.