Although topic sentences may appear anywhere in a paragraph, in academic essays they usually appear at the beginning. It helps to think of a topic sentence functioning in two different directions at the same time. It links the paragraph to the thesis of the argument, and acts as a reminder of your position, and also identifies the scope of the individual paragraph.
For example, consider the following topic sentence:
“Captain Smith’s responsibility for the sinking of the Titanic was due to a number of errors of judgment which contributed to the collision with the iceberg.”
If this sentence identifies the scope of the paragraph that follows, then all other sentences in the paragraph must connect in some way to “Captain Smith”, “Responsibility”, and “Errors of judgment” and “Collision with the iceberg”. So, the next sentence might be “Despite warnings of icebergs, Captain Smith decided to comply with the wishes of the owner of the White Start Line, Bruce Ismay, to continue ahead at full speed.” This sentence fits in with the topic sentence because it relates to the Captain and an error of judgment.
“In addition, the Captain went to bed leaving his Second-in-Command in charge, when dangers had already been highlighted.”
The transitional phrase “In addition” relates to another possible error of judgment that could have influenced the collision. Obviously, the Captain cannot be on the bridge all the time over 6 days, but the choice to retire at this time could be a contributing factor.
Finally, the paragraph finishes by “proving” the claim contained in the topic sentence, “Captain Smith was ultimately responsible for the safety of his passengers and crew, and could not be dictated to by his employer if the request endangered the ship.”
A sentence that you might be tempted to include would be “The Captain failed to ensure that all crewmembers were trained in the use of lifeboats.” This is relevant to the essay, in that it addresses one of Captain Smith’s oversights, but it is not relevant to this paragraph, as the oversight did not cause the sinking of the ship. A more appropriate sentence to include would be “The Captain failed to ensure that binoculars were available for all lookouts.”
So, a good topic sentence can enhance an essay’s readability and structure. The points to consider when creating your topic sentence are:
Topic sentences can be like mini thesis statements. Similar to your thesis statement, a topic sentence makes a sort of claim. Just as the thesis statement is the amalgamating force behind the essay, so the topic sentence must be the unifying element in a paragraph. Additionally, as happens with the body of the argument after the thesis statement, the paragraph following a topic sentence should expand, describe, or prove it in some way. A topic sentence will make a point that lends itself to being supported by evidence or a rationale.
Take the paragraph above as an example of a mini thesis statement, which starts with the topic sentence: “Topic sentences can be like mini thesis statements.” This is the claim, or the point that the paragraph will support. All the sentences that follow this topic sentence relate to it in some way. The next two sentences show how you, the reader, can compare thesis statements and topic sentences “Similar to your thesis statement, a topic sentence makes a sort of claim. Just as the thesis statement is the amalgamating force behind the essay, so the topic sentence must be the unifying element in a paragraph.” Next in the paragraph, I wrote “Additionally, as happens with the body of the argument after the thesis statement, the paragraph following a topic sentence should expand, describe, or prove it in some way”. Here, I used the transitional word “Additionally” to link the sentence to the preceding sentences and expand on the topic sentence. Finally, the paragraph concludes by showing precisely how topic sentences behave like thesis statements. “A topic sentence will make a point that lends itself to being supported by evidence or rationale.”