Excerpted from newrepublic.com:
The divergence between my description of historical events and the accounts of historians … is not accidental but inevitable. A historian and an artist, describing a historical epoch, have two completely different objects. As a historian would be wrong if he should try to present a historical figure in all his entirety, in all the complexity of his relations to all sides of life, so an artist would not fulfill his task by always presenting a figure in his historical significance. Kutuzov did not always ride a white horse, holding a field glass and pointing at enemies. Rastopchin did not always take torch in hand and set fire to his Voronovo house (in fact he never did it at all), and the empress Maria Feodorovna did not always stand in an ermine mantle, her hand resting on the code of law; but that is how they are pictured in the popular imagination.
I can't understand the bolded sentences, I read this as the following:
As [ a historian would be wrong if he should try to present a historical figure [ in all his entirety... to all sides of life ] ], so an artist would not fulfill his task by always presenting a figure in his historical significance.
But then its meaning is odd, it suggests a historian shouldn't present a historical figure in all his entirety, but which I think by common sense he should. Furthermore, the latter part suggests an artist would not do what a historian does, and he does this by always presenting a figure only in his historical significance, but this contradicts to what the first half suggests, it suggests historian shouldn't try to present entirely, hence should present only in historical significance, which is exactly what the latter half says an artist does!
The only possibility for it to be coherent is a historian should present a historical figure in all his entirety, but I don't see how the original context could mean it. So what exactly does these mean?