There are four parts to the I.R.I. theme. The first part is illusion (what seems to be.) The next one is reality (what is.) The last part is ideal (what should be.) It should be perfect, moral, and be in God's way. The fourth part is the artist. The artist exposes illusion by showing the reality. Their disillusions can be either bad or good. When they are bad, we don't like it and it tends to make life harder. When it is good it moves us toward the idea and makes us better people.
Romanticism is emotion as opposed to reason. Characters act out of emotion instead of reason. We approach the story on a level of emotion not realistically. We suspend disbelief. Nature can effect our emotions as in storms and foggy weather. It can also speak to us through symbols that are tangible. This represents something abstract, or ideal.
We also experience these through our senses. The third part of romanticism is supernatural, unusual, gothic, exotic, and grotesque. The fourth is mythology and folklore (Greek and Roman). The fifth part is emphasis on self reliance and independence. Which are the characters. The last part is nationalism. We use these themes to comprehend the story we read better.