Themes vs topics in history

I am sorry for the delay in posting here. I have continuing computer problems.

One of the things that I have been mulling over in the context of my general history of New England is the question of themes versus topics.

I was reading some material on New England architects. I need this because I need to be able to explain details of the built environment. However, I don't want to devote a separate section to architects as such. Rather, I want to build the material into the general discussion.

It's not that architects and architecture are nor important, they are. It's just that in a broad history I don't want to focus on them as such. This led me to make a distinction between themes and topics.

To my mind, a theme is a broad unifying element that crosses time. By contrast, a topic is something that supports a theme, but which may appear in different forms with different themes and may cross themes.

Squatting is a theme. As they became established and more secure, they built big houses designed in many cases by architects. From this perspective, architects are a topic that links to one or more themes.

All this may seem a bit arcane, but I am struggling with the best way of organising a mass of material.

Having overrun my original target for completing the book by a considerable margin, I have now set a new first draft completion date of 20 December. To do this, I need to be far more organised than I have to this point!