what the theme of gulliver's travels story

There are too many themes to discuss for this forum. There is the human body. Swift is not shy about bodily functions! There is Literature and language. Gulliver spends much time reading and interpreting the various societies by their linguistic attributes. There is always a strong sense of "otherness". Gulliver never fits into any of the societies that he visits so the "fish out of water" theme resonates throughout the novel. This enables him to lend a sense of objectivity to a given situation. There are more but instead of babbling on, I'm just going to give you a link with the GradeSaver page that better details your query than I can in this forum.