Final answer:
The major theme of St Bernard's writings was religious devotion and spirituality, emphasizing the importance of personal piety, prayer, and contemplation.
Step-by-step explanation:
St Bernard of Clairvaux was a theologian and writer during the Middle Ages. The major theme of his writings was religious devotion and spirituality. He advocated for a simpler and more contemplative approach to Christianity, emphasizing the importance of personal piety, prayer, and contemplation. He believed in minimizing distractions and focusing on the direct experience of God. His writings often discussed themes such as the love of God, the pursuit of holiness, and the contemplation of divine mysteries.