I borrowed money and when I tried to pay the agreed amount back, the creditor refuses, claiming the peso has lost so much value — what law governs my obligation?

Money loans are governed by a specific pair of articles

Article 1955 does not set its own separate rule for money loans — it points you directly to two other provisions: "the obligation of a person who borrows money shall be governed by the provisions of articles 1249 and 1250 of this Code." That means the answer to your question is found in those two articles, not in some separate, more forgiving rule for currency depreciation that applies only to loans.

The ordinary rule: pay the stipulated amount in stipulated currency

Article 1249 sets the baseline: "the payment of debts in money shall be made in the currency stipulated, and if it is not possible to deliver such currency, then in the currency which is legal tender in the Philippines." Ordinary changes in the peso's purchasing power over time — inflation in the everyday sense — do not by themselves change how much you owe. You generally satisfy your obligation by paying the agreed nominal amount in the agreed or legal tender currency.

When the creditor might have a real argument: extraordinary inflation or deflation

The creditor's refusal only has legal weight if Article 1250 actually applies: "in case an extraordinary inflation or deflation of the currency stipulated should supervene, the value of the currency at the time of the establishment of the obligation shall be the basis of payment, unless there is an agreement to the contrary." This is a narrow, exceptional rule — it requires an extraordinary change in the currency's value, not the ordinary loss of purchasing power that happens over time in any economy. Whether the depreciation the creditor is pointing to actually rises to that level is a serious factual question, not something either side can simply assert.

What this means for resolving your dispute

If your loan agreement did not stipulate any adjustment for currency fluctuations, and the depreciation involved is the kind of gradual change ordinary economic conditions produce, Article 1249 supports your position that tendering the agreed nominal amount discharges your debt. The creditor bears the burden of showing that the currency's decline was genuinely extraordinary before Article 1250 can justify demanding more than what you agreed to pay, and the parties can also always agree between themselves on a different arrangement.

Related provisions

• Civil Code, Article 1955 — Obligation of the Money/Fungible Borrower
• Civil Code, Article 1249 — Currency of Payment; Payment by Instruments
• Civil Code, Article 1250 — Extraordinary Inflation or Deflation