Snellen defined standard vision as the ability to recognise a letter (âoptotypeâ) when it forms an angle of 5 arcminutes, which is âline nineâ of the letters (âoptotypesâ) on the chart at 6 metres. Hermann, Dutch ophthalmologist, 1834-1908.
In the context of the theory of Marxist revolutionary struggle, vanguardism is a strategy whereby the most class-conscious and politically advanced sections of the proletariat or working class, described as the revolutionary vanguard, form organizations in order to draw larger sections of the working class towards revolutionary politics and serve as manifestations of proletarian political power against its class enemies.
The terms radical centrism, radical center (or radical centre) and radical middle refer to a political ideology that arose in the Western nations in the late 20th century. At first it was defined in a variety of ways, but at the beginning of the 21st century a number of political science texts gave it a more developed cast.