Short answer. It depends on importance. Article 1264 says the courts shall determine whether, under the circumstances, the partial loss of the object of the obligation is so important as to extinguish the obligation. You are not automatically released; a court weighs how significant the lost part is.
What the law says
The courts shall determine whether, under the circumstances, the partial loss of the object of the obligation is so important as to extinguish the obligation.
Civil Code, Article 1264 — Partial Loss. Read the full provision →
Partial loss does not automatically release you
When the specific thing you owe is only partly destroyed, the law does not treat that like a total loss that ends the obligation outright. Article 1264 puts the judgment in the hands of the court: The courts shall determine whether, under the circumstances, the partial loss of the object of the obligation is so important as to extinguish the obligation. The obligation is not automatically extinguished, and it is not automatically kept alive either. Instead, whether you are released turns on how significant the destroyed portion is relative to the whole — a question the article assigns to judicial evaluation rather than to any fixed formula.
The test is the importance of what was lost
The operative words are so important as to extinguish the obligation. A court looks at the circumstances: what part was lost, what remains, and whether the remaining portion still answers the purpose of the obligation. If the lost part is essential — so central that what survives is no longer substantially what was owed — the obligation may be treated as extinguished. If the loss is minor and the core of the thing endures, the obligation generally continues, perhaps with the delivery of what remains. Importance, not mere percentage, is the measure, and it is judged against the specific object and the parties' purpose.
The loss must be accidental
This rule is meant for a loss you did not cause. It fits a partial destruction by fortuitous event — an accident without your fault and outside your control. It does not shelter a debtor who is at fault, who is in delay, or who has agreed to bear the risk; in those situations other provisions can keep you liable, including for damages, despite the loss. So before reaching Article 1264's importance test, it matters that the partial loss was genuinely accidental. If the destruction is traceable to your negligence or breach, the article's possibility of extinguishment does not simply erase your responsibility.
What this means for you
Do not assume that because part of the thing survived you must still deliver, and do not assume that because part was destroyed you are free. The realistic position is in between: your release depends on a reasoned assessment of how vital the lost portion was. Where the remaining part still serves the obligation's purpose, expect that you may be held to deliver it; where the essential portion is gone, extinguishment becomes possible. Because the outcome is fact-sensitive and, by the article's own terms, one the courts decide, the specific nature of the thing and the extent of the loss will drive the result.