Socialism, if it means anything, is the rational attempt to have equality govern people's relations to one another---although individuals are not equal.
No Marxist has ever claimed (as enthusiastic utopian socialists, such as Robert Owen did) that all individuals are equal in aptitude, intelligence, or physical strength.
Speaking of the socialist principle, 'from each according to ability, to each according to work,' Marx clearly acknowledges unequal abilities:
[The principle 'from each according to ability, to each according to work'] recognizes no class differences, because everyone is only a worker like everyone else; but it tacitly recognizes unequal individual endowment and thus productive capacity as natural privileges.(1)
Going a step further, Lenin:
When we say that experience and reason prove that men are not equal, we mean by equality, equality in abilities or similarity in physical strength and mental ability.
It goes without saying that in this respect men are not equal.(2)
Lenin, however, submits that there are two different types of equality: equality of abilities and, in contradistinction, equality of rights.
Equal abilities speak for themselves (a biological impossibility). Equal rights, however, means the abolition of classes (a political possibility).
The abolition of classes means placing all citizens on an equal footing with regard to the means of production belonging to society as a whole.(3)
This is the equality Marxists speak of when they speak of equality.
That said, it may be asked: wouldn't job rotation (worker control of the workplace and the state) attempt to negate the natural differences in individual's abilities?
To some degree, yes.
There is no doubt that a doctor (the popular example of exceptional individual ability), if required to perform unskilled jobs as well as perform medical duties, would be required to do less of the work he / she does best. Likewise: there is no doubt that a governor (a less popular example of exceptional individual ability), if required to perform unskilled jobs as well as perform tasks of governance, would be required to do less of the work he / she does best. And that particular example best demonstrates WHY a society would want job rotation: to insure that those who make decisions that affect others will also affect themselves.
That is the best guarantee that decisions will be made with the utmost consideration for ALL people.
And that issue transcends equality of ability. It is a fundamental issue of equality of rights.
1. Marx, Critique of the Gotha Programme, International 1938, p. 9.
2. Lenin, 'A Liberal Professor on Equality,' Collected Works, Progress 1964, p. 144.
3. Ibid., p. 146.