The monster is at first a Romantic, then he becomes a Rationalist.
Frankenstein's mother served as a warning sign against Rationalism. It can be assumed that a wise and strong woman in her deathbed would speak of significant matters in her last moments. She had the older generation's ideas on love. Society is facing trials of Rationalism and Romanticism till today. It is a particularly heavy struggle for the human psyche and the attainment of mass media, knowledge, and social hubs has made those involved in popular culture delve deeper within themselves and their thought process.
Mary Shelley favoured wrote Frankenstein to display the characteristics of Modern Rationalism and Romanticism. She did not lean towards one belief.