Dishonesty
Jacob, the main character of Jacob the Liar, is modeled after the Biblical Jacob, who lies to his father in order to secure his blessing, though his father intended to bless his older brother. Jacob's mother had received a prophecy while pregnant saying that Jacob's older brother would serve him; thus, Jacob's deception—which is aided by his mother—may not have been altogether immoral, as it may be viewed as carrying out a covenant with God. Similarly, Becker casts Jacob Heym's lying as morally ambiguous.
Jacob first lies to prevent Mischa from endangering himself by stealing potatoes. He continues to lie when he sees how it gives the residents of the ghetto hope and reduces suicides. Characters in the novel consistently lie to protect each other and survive in difficult situations. In such contexts, is lying wrong? This is a central question of the text.
The Absurdity of War
The narrator's comic tone mirrors the fundamental absurdity of a situation in which the Russian army seems to be advancing while absolutely nothing changes. Becker uses these elements to suggest that the Nazi campaign, which sparked the entire situation, is the root of this absurdity.
Take, for example, the case of the lawyer, Leonard Schmidt. Schmidt had been a respected and successful lawyer who was "well on the way to becoming a German nationalist" when it was discovered that he had Jewish heritage, and he was arrested. The case of Leonard Schmidt serves to demonstrate Becker's larger point, that the Nazi campaign was inherently absurd.
Humanity
Becker suggests that everyone is alike through the condition of being human, and that power only serves to obscure this connection. Nazis in the text occasionally show moments of humanity. For example, the duty officer sends Jacob home at the beginning of the novel instead of punishing him arbitrarily. Additionally, a soldier drops cigarettes for Kowalski, apparently as an apology for beating him. These moments of humanity are in a sense at the heart of the text. They allow the reader to imagine a world in which people were not divided by their differences but united by their similarities. Becker offers this way of life as a model for the human race.
Hope
Jacob's radio reports give the other residents of the ghetto the hope they need to persist in their lives, yet it is a hope that is ultimately based on lies. Becker forces the reader to consider the value of this hope, as, in Jacob's own words, "'the Russians won’t arrive any more quickly'" if the people in the ghetto are anticipating them. And, while the number of suicides in the ghetto drastically declines due to this sense of hope, all the residents are sent to extermination camps anyway. Does hope have value for its own sake? Is it morally right or wrong for Jacob to make people feel hope if his radio reports are baseless? Becker forces the reader to reckon with these difficult questions.
Death
Death is ever present in this text, which is backdropped against the Holocaust and World War II. We learn at the very beginning of the novel that the narrator's wife, Hannah, was executed by the Nazis. After this introduction to the theme, death reaches every character either directly or indirectly. Of the novel's main characters, it is Kowalski and Kirschbaum whose deaths are shown to us most plainly. However, almost all the other Jews—with the notable exception of the narrator—are set to be killed at the end of the text. Even the Nazis are not immune to death in this text, as Hardtloff, the ghetto's head officer, dies of a heart attack in chapter 29.
Family
As a result of the war, families are separated and reconstituted throughout Jacob the Liar. The narrator's family is destroyed before the text's narrative even begins, as he states that "my wife, Hannah, was executed under a tree." Lina's family is also destroyed by the Nazi regime—her parents are deported two years prior to the narrative taking place. Rosa is separated from her parents by another round of deportations, and Leonard Schmidt, Roman Schtamm, and the Kirschbaums are all separated from their loved ones.
Yet, the residents of the ghetto also form new familial bonds as a necessary result of these losses. Jacob takes care of Lina after her family's disappearance, allowing the two of them to become family. In fact, Lina begins to call Jacob "Uncle Jacob." Rosa and Mischa similarly forge a new familial connection with each other as the ghetto separates Rosa from her family. And new relationships are formed even at the Jews' worst moment—the narrator and Lina meet and bond as they are on the train to the extermination camp.
Memory
Jacob the Liar is a text that is preoccupied with the idea of memory. The narration is presented as recollection after the fact, with the narrator often stopping to dwell on events from his own past, such as the loss of his wife. At the same time, the characters in the text are constantly remembering life before the ghetto was instituted, giving this theme a kind of doubling effect. In both cases, memory is painful, providing a reminder of what has been lost. Yet, it can also be a powerful motivation for persisting when things get difficult, as the characters often rely on their memories to imagine what life could be like when the Russians arrive. Similarly, memory and the desire to carry on this memory motivates the narrator to return to the ghetto after the war. He tells us, "On the next to last day of my holiday, I wondered as I was packing whether I had forgotten anything; I would probably never return to this town, and this was the last chance for anything I had overlooked." It is clear from this quote that the narrator's trip to the ghetto is inspired by a desire to remember everything, though it is obviously painful to do so.
