Art discussion

The themes of art can really be condensed to two themes: representation of the natural world (nature) and representation of the intangible. Most themes of pre-20th century art are descended from the theme of nature, while representation of the intangible dominates 20th century art as a theme. Using the two images listed here, explain briefly why one is an example of the theme of nature and the other is an example of the theme of the intangible. 

8th edition:

fig. #4-18, p. 77 Place de l'Europe on a Rainy Day by Gustave Caillebotte

fig. #4-29, p. 85 Color and Information by Terry Winter