Some Thoughts:

World War 1 created a gulf in the seemingly solid period of Modernism. The zeitgeist of 1913 was not the same as in 1920, without a doubt. 1890-1913 was, except for a few exceptions (Oswald Spengler, Georg Simmel), an era of hopefulness. Science and the resulting technology really were making life better for people, and a belief in progress was restored.
After the war, this all fell apart. But it was not because of the war, rather, the war was a symptom of a growing storm.

I set out on this project to define some of the psychological/philosophical characteristics of the period of Modernism. I view history as a dichotomy between reason and intuition. 1890-1913, which I will refer to as 'early Moderism,' was characterized by incredibly rapid advances in science, from physics to psychology to chemistry to medical science. Science was providing answers to fundamental questions that philosophy and religion could not satisfy, though they had tried for hundreds of years. It answered the question of where we came from with the theory of Evolution (which, although published in the 1850s, was not widely accepted until the 1900s). It answered the question of what we are made of with the discovery of genes and atoms. The mysteries of the human mind were seemingly rooted out with the advent of Freud, the unconscious, and the practice of psychology.
The author of Modern Mind places an emphasis on the idea that the modernist thinkers were trying to break reality into 'fundamental units,' as he calls them. Genes, atoms, and, in the realm of art, the Cubism of Picasso, Cezanne and Monet, were all examples of this (I'm sure there are more, but I can't remember them). I'm not quite sure what to make of this, but it is an interesting trend. These are just a few of my observations.
Science is the epitome of reason. In the late 1800s, science was seen as the savior of humans. One woman went so far as to say that "science will wipe away all human misery." But did it do that? My tentative answer to that would be no, as evidenced by the later period of Modernism, which seems to me to be characterized by a loss of faith in the possibilities of science, and, related to science, the idea of progress. The concept of progress is rooted in reason. As our understanding of the physical world advances, we should be making progress toward creating a better, happier, healthier, cleaner world. This is a very logical viewpoint. In contrast to this is the view that, fundamentally, we are no better off now than we were 100 years ago, or 200 years ago, or even 1000 years ago. In the 1920s there was in interest in history. Old barriers related to Eurocentricity were being thrown off; Christianity was revealed to be just another religion among many, no more complex or valid than Islam, Buddhism or Hinduism.

Religion is a decidedly intuitive aspect of culture. It requires a leap of faith that is not logical at all. So, if I had to measure the ratio of reason to intuition in the period of early Modernism, I'd say they were high on reason but low on intuition. And I'd say this is actually a bad thing. The horrors of WW1 were the catalyst in destroying the populace's faith in scientific progress. In a world that was supposedly so perfect, how could such a long, taxing, and needless war break out? Science had been tested, for 25 years, and it had proved itself to be insufficient at "wiping away all human misery," as that woman predicted in the 1880s.