After completing a reading, one can make many different inferences regarding Mary Shelley's Frankenstein. In order to do this, one must first understand the concept of inference (or inferring). An inference is when one makes conclusions about something given the information presented. For example, when a high school student arrives home after school, and the door is locked and all lights are off, the student can infer that no one is at home. That said, literary inferences are sometimes a little harder to make.
One inference one can make can be found in Letter Four of Mary Shelley's Frankenstein. Robert Walton, the narrative voice of the novel, is traveling to the North Pole in order to find the seat of magnetism and a faster passage of travel for sailors. During his journey, Walton comes across a half-frozen man. The man begins to tell Walton about how he has come to be alone on the ice. Readers infer that the man Walton has picked up is Victor Frankenstein.
Outside of individual inferences readers can make while reading the novel, many different inferences can be made upon the novel's completion. First, one can infer that the novel serves as a warning to readers. The warning provided makes readers think about the pursuit of forbidden knowledge. Given that Victor's creation of the creature leads to both his death and the death of many others, readers can infer that some knowledge must remain unknown to mankind.
Second, one can infer that Shelley's novel speaks to the powerlessness of women (at least during the period which it was written). All of the female characters (Caroline, Justine, the female creature, and Elizabeth) die. Victor even takes the power of birth away from women.
Third, one can infer that nature proves to be the most powerful "being" on the planet. Given that the novel is Romantic, Shelley includes many references to the power of nature over mankind--most notably, Victor's need for the rejuvenating power of spring during his multiple recoveries from illnesses.
Even after these suggestions regardling inferences made, each individual reader should come away from any novel with a deeper understanding of what the author wished the reader to learn about. Paying close attention to themes of a novel help.