Emiko, most academic texts are written in a very special and dense type of text and as Adrian says it can be difficult to gain the full meaning! Let's take the first sentence from On Liberty and rewrite it in 'normal' English. "The subject of this Essay is not the so-called Liberty of the Will, so unfortunately opposed to the misnamed doctrine of Philosophical Necessity; but Civil, or Social Liberty: the nature and limits of the power which can be legitimately exercised by society over the individual. ." This essay is not about the Liberty of the Will, which is against the incorrectly named doctrine of Philosophical Necessity. It is about Civil or Social liberty, these are the powers which control an individual. It has taken me some time to rewrite just this sentence into language which could be understood so it will definitely not be easy for a non-native speaker and there are still some technical terms that you would need to check the meaning of! You could have a look ar something like sparknotes http://www.sparknotes.com/philosophy/onliberty/section1.rhtml This will save you having to struggle with the heavy language in the original. Hope this helps Bob.

You're right - native speakers also find this style of writing turgid and difficult. The subject in each sentence is probably there, but takes some 'digging out'. While it is useful to be able to refer to the original source material if necessary, most students today will probably be using more recent textbooks for easy reference.