The Binding of Isaac is a rogue-like video game, meaning that each run is completely separate — dying or completing the run both reset your character, so you have to restart from a fresh slate. However, your progress through each run is accounted for, and when certain acheivements are completed future runs might change. This mechanic allows the developers of the Binding of Isaac to tell a story through game completions, with different goals presenting different endings. Some of these endings, especially the ones that progress the plot, can be analyzed to display Isaac’s tragic childhood.
Epilogue (Ending 0)
After you defeat Isaac’s mom, a crudely drawn cartoon of the events that just occurred is displayed. However, after God intervenes and stops the mother, the camera pans out to a happy, more realistic Isaac, whose smile quickly turns to terror when he realizes his mom has come to kill him. This is the largest example of the events of The Binding of Isaac merely taking place in Isaac’s imagination, and also shows his desire to stop his mom, who has probably been abusing him. This ending unlocks Mom’s heart, the next boss.
After you defeat Mom’s heart for the first time, the new character Eden is unlocked. The character is shown to be very diverse, and as such represents Isaac’s creative side coming out in another one of his personalities.
After you defeat Mom’s heart for the second time, Isaac unlocks rubber cement. This is more of the video game side of the game displaying itself, although it does show that Isaac is young, as some toddlers get into things they shouldn’t quite often.
After you defeat Mom’s heart for the third time, Isaac discovers a rope and hangs himself with the item, which is gruesomely named Transcendence in-game. This emotional state is reached when a huge accomplisment is reached or a new level of existance is achieved, implying the events of Isaac’s life have left him suicidal. This ties into the theory that Isaac blames himself for his parent’s separation, as he feels he tore his family apart.
After you defeat Mom’s heart for the fourth time, Isaac discovers a coat hanger and impales himself through the head. This item continues the abortion theme seen throughout the Binding of Isaac, as wire coat hangers are occassionally used to perform bloody, unsafe abortions. Additionally, the fact that Isaac gets the object through his head could mean he wishes the other characters in his head could go away, and the vague rumors of abortion he might have heard make him believe impaling himself could help.
After you defeat Mom’s heart for the fifth time, Isaac opens the chest to find his mother waiting for him. This is fairly obviously his imagination explaining what has happened — his mother has discovered his actions, and will make things even harder for him. This could imply she has found his drawings, meaning it will be a lot harder for him to continue his stories. As such, the achievement Everything’s Terrible is unlocked, making the game have a much higher difficulty.
After you defeat Mom’s heart for the sixth time, Isaac discovers Ipecac in the chest. This is another video game cutscene, although Ipecac is a real life medicine used to induce vomiting, similar to the in-game effect.
After you defeat Mom’s heart for the seventh time, Isaac discovers a strange syringe and injects himself, with clear signs of problems arising from this. Once again, this cutscene is another example of Isaac being a kid and playing with hazardous things.
After you defeat Mom’s heart for the eighth time, Isaac discovers a quarter in the chest. This is a prime example of Isaac being a young child — 25 cents means a lot more to an innocent youth than it does to a religious figure. This provides another clue to the fact that the Binding of Isaac takes place in his imagination.
After you defeat Mom’s heart for the ninth time, Isaac discovers a fetus in a jar. This fetus is actually a strong familiar, and one of the prime examples that Sister Maggy and Brother Bobby are also fetuses representative of Isaac’s siblings. This game has a large focus on the fetal stage of life, and Epic Fetus is no exception.
After you defeat Mom’s heart for the tenth time, Isaac opens the chest to discover another playable character and boss, ??? (fans know him as Blue Baby). As with Eden, Blue Baby is covered extensively in the characters section of this Binding of Isaac collection.
After you defeat Mom’s heart for the eleventh time, Isaac opens the chest and finds nothing, but discovers that behind him is his mother’s heart, reborn again. After taking so much punishment, the heart becomes a much more fearsome enemy. In my opinion, It Lives represents Isaac’s mom’s emotions after discovering the many drawings that her son has created. She is overcome with the emotion of discovering time and time again that Isaac truly sees her as a monster and nothing else, and as such becomes distraught. Her emotions towards Isaac become much stronger, possibly to the extent of what drove her husband away.
After you defeat Isaac himself in the Cathedral, Isaac flashes through his personas (Cain, Magdelene, Judas, Eve, Azazel), and finds himself in his room. The character you defeat Isaac with unlocks a certain item. However, this scene concludes with Isaac getting into the chest in his room, further strengthing the fact that the events of the Binding of Isaac are simply in Isaac’s imagination. He looks quite sad getting into his chest due to the fact that you just defeated Isaac himself, which might mean his psyche has finally broken. Fans of the old Binding of Isaac game speculated that this scene represents Isaac getting ready to commit suicide, seeing as he has been completely broken in spirit. However, Binding of Isaac: Rebirth helps to dispel this myth, but does imply Isaac’s spirit has broken with the unlocking of the Chest, the next part of the story.
After you defeat Satan in Sheol, Isaac finds himself dealing with his own demons, as his experiences have told him to side more with the sinners. He seems to accept this fate, as this scene unlocks the next part of the story: the Dark Room, where Isaac fights more demons on his own.
A direct sequel to Ending 12, Isaac defeats the Blue Baby in the Chest, revealing a touching montage in which polaroids display Isaac’s family falling apart without any supernatural events occurring. This sad tale is able to be shown due to Isaac confronting the Blue Baby, which represent his fears that his family wishes he were never born similar to his potential brother Bobby. The polaroids allow insight into Isaac’s life without his colorful imagination and drawings.
A direct sequel to Ending 13, Isaac is able to defeat the Lamb in the Dark Room. In the original biblical story, Isaac pleads with Abraham to sacrifice a lamb instead. Isaac’s imagination created a lamb in his mind to take down in order to confront his own demons, which he was able to defeat. Afterwards, we flash back to real life, where we see that Isaac has been able to escape his household and his religious mother, whose horrifying sillouette is seen in the background of the scene.
The most horrifying ending and the alternate sequel to ending 12. Isaac was able to defeat Mega Satan, but finds himself struggling to overcome his own demons due to his new power. You can hear Isaac’s breathing get more and more shallow, with a wheeze at the end becoming a demon’s heavy breathing. This is the most direct route to showing Isaac unable to overcome his mental issues, giving in and going insane. The demons he had imagined in his mind were able to overtake it and become his reality, the first and only real crossover between the two realms. Isaac’s fate is doomed as he loses his sense of self-identity to the monster he has been lead to believe he has become.