One might ask what value there is in studying a 'definite trend in the historic development of mankind' that does not articulate a specific and detailed social theory. Indeed, many commentators dismiss anarchism as utopian, formless, primitive, or otherwise incompatible with the realities of a complex society. One might, however, argue rather differently: that at every stage of history our concern must be to dismantle those forms of authority and oppression that survive from an era when they might have been justified in terms of the need for security or survival or economic development, but that now contribute to---rather than alleviate---material and cultural deficit. If so, there will be no doctrine of social change fixed for the present and future, nor even, necessarily, a specific and unchanging concept of the goals towards which social change should tend. Surely our understanding of the nature of man or of the range of viable social forms is so rudimentary that any far-reaching doctrine must be treated with great skepticism, just as skepticism is in order when we hear that 'human nature' or 'the demands of efficiency' or 'the complexity of modern life' requires this or that form of oppression and autocratic rule.
I was attracted to anarchism as a young teenager, as soon as I began to think about the world beyond a pretty narrow range, and haven't seen much reason to revise those early attitudes since. I think it only makes sense to seek out and identify structures of authority, hierarchy, and domination in every aspect of life, and to challenge them; unless a justification for them can be given, they are illegitimate, and should be dismantled, to increase the scope of human freedom. That includes political power, ownership and management, relations among men and women, parents and children, our control over the fate of future generations (the basic moral imperative behind the environmental movement, in my view), and much else. Naturally this means a challenge to the huge institutions of coercion and control: the state, the unaccountable private tyrannies that control most of the domestic and international economy, and so on. But not only these. That is what I have always understood to be the essence of anarchism: the conviction that the burden of proof has to be placed on authority, and that it should be dismantled if that burden cannot be met. Sometimes the burden can be met. If I'm taking a walk with my grandchildren and they dart out into a busy street, I will use not only authority but also physical coercion to stop them. The act should be challenged, but I think it can readily meet the challenge. And there are other cases; life is a complex affair, we understand very little about humans and society, and grand pronouncements are generally more a source of harm than of benefit. But the perspective is a valid one, I think, and can lead us quite a long way.
Beyond such generalities, we begin to look at cases, which is where the questions of human interest and concern arise.