Isaiah Berlin is a 20th century philosopher of Latvian-Jewish descent and British education who has wrote extensively on personal and political liberty. It is clear and obvious from these essays (many derived from the lectures he gave at Oxford in the 50s-60s) that Berlin is well acquainted with the vast western philosophical literature that has accumulated over millennia.
"Political Ideas in the 20th Century" is the first and probably the most striking of his essays collected in this book. In this he principally covers the development of the two dominant ideologies after the Second World War: Liberalism and Socialism/Communism. While different in many respects, liberalism and socialism are both fundamentally rationalist ideologies who believe in reason and the conviction that societal issues can be solved if intelligent people of the right virtues triumph over the ignorant and evil (as opposed to the romantic nationalists/fascists, who appeal more to the emotional and spiritual character of people). However, the pursuit of reason over ignorance came with it uncomfortable questions for both ideologies that did not have clear-cut answers: what is an individual's purpose in society? What responsibilities do the majority have for the minority? What responsibilities do the minority have for the majority? How are competing interest claims to be balanced against one another? These questions do not have easy solutions, in fact they might not ever be solved. Instead, Berlin witnesses a frankly terrifying trend amongst all societies east and west to ignore these issues entirely as irrational nuisances to the rule of the just. Over his life, Berlin saw the power to control society centralized increasingly into fewer hands of state and corporate administrators, experts and busy bodies to a degree that would have seemed utopian not too long ago. Onlookers in Britain and America who still clung to 19th century visions of political life looked on in horror at Europe as both men and masters alike agreed on a consensus that liberty should be handed over for the sake of increasing control over every part of life. The current year is 2025, and I feel like what Berlin has described has not stopped.
"Historical inevitability" concerns determinism as a way of viewing the world and its impact on how we view the freedom of individuals. Are we destined to do what we have done/do/will do? Berlin thinks that there is no real way to disprove determinism (after all, one would need a time machine to see whether destiny really does exist) but rejects it nonetheless. His main contention seems to be that determinists do not actually think deterministically, and for determinism to actually be true would require a complete restructuring of how we view the world. We cannot ascribe praise or blame to people because everything would simply be a result of background factors and not the people themselves. A criminal cannot be persecuted if in reality we are blaming whatever socioeconomic factors caused him to commit crime, but we too cannot blame a rich man for exploiting others if that was what he was determined to do. Likewise, we cannot say "I should have/should not have done that" because we were never free in the first place to do so. Obviously people are influenced by several different factors when we make decisions, which Berlin acknowledges, but to leave everything to the explanation of "factors" would, in my opinion, render society incapable of governing itself as it would treat every person like a child, unresponsible for their own actions.
"Two Concepts of Liberty" talks about negative and positive freedom. Berlin describes negative freedom as "how far am I controlled" and positive freedom as "who controls me." Berlin seems largely concerned though with refuting those who emphasize positive freedom, as he sees it as responsible for some of the worst abuses and dictatorial regimes of the 20th century. He sees positive freedom as something that usually incorporates with it the idea that there is an ideal, objective end to be pursued by all people but which only a few are aware of. These enlightened few must guide the rest of humanity, regardless of their objections, to this end to achieve their true self. This, according to Berlin, is at the core of most ideological dictators' rationales for their power. I shall leave others to dispute Berlin on this. Additionally, it is just impossible to solve positive freedom completely. One can be completely absent of restraints (negative freedom) but one is always oppressed by the physical and psychological processes of life. Overemphasis leads to suicide being the only way to achieve true positive liberty.
"John Stuart Mill and the Ends of Life" is a neat though not altogether controversial (at least to me) essay on JS Mill and his commitment to liberty as an end. He recounts Mill's early life, where he was surrounded by Benthamite utilitarians who preached the God of utility. However, despite Mill being at times associated with the utilitarian movement, Berlin argues through Mill's political life and writings to be committed to liberty above all, and that he made a constant stand against utilitarianism.
"From Hope and Fear Set Free" is a sort of bonus essay included in the book and a relatively simple one. Some have advanced that knowledge and liberty go hand in hand. Berlin objects to this, and states that knowledge can at times be a hindrance on one's liberty. Berlin identifies the sometimes illogical views of logical men to tie knowledge inseparably with liberty to be a result of a view held by many that all that is good in the world must not seriously conflict with one another. Things we may deem good however, like liberty, equality, security, or in this case, knowledge, are not always in agreement with one another. I agree.
The book includes other writings by Berlin but these are the main essays that frame his principal views on liberty. It also has another essay by him about the birth of Greek individualism, wherein he describes the transition in Ancient Greek from the polis-oriented worldview of Plato and Aristotle to the personal, introspective worldviews of the epicureans and stoics. Suffice it to say that I find this book gives a lot to think about.