The primary themes of the Enlightenment era that impacted European thought included reason, individualism, and questioning authority. Philosophers like John Locke and Voltaire argued for the application of reason in understanding human behavior and governance. The movement encouraged a shift away from tradition and religious authority, promoting ideals of democracy, scientific inquiry, and human rights. These themes laid the intellectual groundwork for revolutions and social changes, influencing political systems and societal norms well into the modern era.