This is the term usually given to a period in history starting in the 17th century. It is usually regarded as laying the foundations for the 'Enlightenment' of the 18th century.

You can see the beginnings of the Age of Reason in the foundation of bodies such as the Royal Society in England, for the advancement of science, and the rise of philosophers such as Hobbes, Descartes, Pascale and Locke. Overall these thinkers were characterised by a wish to solve problems using logic and rationality; in particular, rationalism, developed by Descartes and Spinoza among others, tried to separate reason from emotions and the senses.

One cause for the popularity of this reliance on calm, unemotional logic was the terrible upheavals caused earlier in the 17th century in Europe by religious fanaticism and superstition. In some countries including Britain, early in the century large numbers of people were burned to death on accusations of witchcraft, for example. Events like these made many people suspicious of religious and superstitious beliefs, preferring to apply a more level-headed approach.