Answer:
The communication tool that spurred the spread of ideas in the 1400s was the printing press, that was invented in that century allowing ideas to spread rapidly.
Explanation:
Until 1453 knowledge was transmitted through manuscripts made by monks: with the invention of the printing press the copying process accelerated and in a matter of a few years the writings covered a huge audience thanks to the diffusion of knowledge and the cheapening of the costs of production.
Basically the invention of the printing made possible the multiplication of texts in the Middle Ages: when the publication of books was very restricted, it revolutionized the culture by expanding the number of potential readers by multiplying the number of books and reducing their cost, so that literacy received a huge boost, never seen before.
The printing press was the most important revolution against the absolute powers (monarchies and church) as it spread knowledge, something that these powers kept for themselves during the ten centuries that lasted the Middle Ages.
