Modernism in its broadest sense refers to the prevailing philosophy underpinning Western European culture since the Enlightenment (or as my old Theology lecturer liked to call it, 'the Endarkenment'). As such it has been around for a long time.

The features of Modernism include:
- a high regard for Reason and the Western Philosophical traditions going back two and a half thousand years to Socrates.
- a movement from the God-centered universe of late medieval times to a Man-centered universe where Man becomes 'the measure of all things' and the measurer of all things.
- Ramism in logic, Objectivism (or pseudo-Objectivism) in philosophy and theology (cf Hegel) and Empiricism in Science.
- a tendency towards Materialism and the rejection of anything existing beyond the known senses. Modernism generally speaking doesn't like allowing for Mystery or admitting that there are things that 'science' can't comprehend.
- a focus on 'the Big Picture' rather than the diverse parts. Modernism likes to imposes structure and meaning on the universe and organise data into patterns that show cause and effect on as large a scale as possible. Modernism desires a harmony of the parts into a coherent whole. Postmodernism on the other hand 'focuses' (not quite the right word) on the diversity of the universe and consciously rejects the search for a wider meaning, preferring to see the universe as a multiverse that doesn't necessarily need reconciling within itself into coherent logical patterns.

Post-modernism is still too young (and perhaps too amorphous) to say whether it is truly a transition to a new philosophical age or just a short term trend, but as a generalisation, people over about forty years of age tend to think in more Modernist terms than the younger generations.

The Baby Boomers, Generation Jones (or the Tweeners as they are also known), and the older Gen-Xes prefer 'Big' things, big causes, universal categories, objective truth, absolutes, capital 'R' Reason, etc. The big no-no for Modernists is being irrational and unscientific. Their big epistemological questions are "Is is True?" and "Can I believe it?"

Postmodern generations, on the other hand, tend to glorify the small and local rather than the big and national and universal. Their outlook is tribal more than democratic, experiential more than scientific, emotional more than rational, 'spiritual' more than materialistic, subjective more than objective, animist rather than humanist, holist rather than compartmentalist. The postmodernist is more likely to be concerned more with the reality of relationships within her own little group of friends than with abstract big picture concepts like World Peace. The big no-no for post-Modernists is intolerance, since there is not one truth but many truths and what is true for you may not be true for me. Live and let live. They are pragmatists not theorists, and if they had big questions rather than a lot of little questions, these would be "Is it Real" and "Can I live it?"

That is a fairly brief summary and contains many generalisations. It should only be applied as such. No one is wholly one or the other, and indeed any particular individual will be affected in their worldview by many different philosophical, relational, religious, social and personal factors. Such tags are descriptive, not prescriptive. A bit like human social grammar.