G.R. No. 5921 - Standard Oil Company of New York vs. Villanueva

On December 15, 1908, Juan Codina Arenas and Francisco Lara del Pino, as principals, and Alipio Locso, Vicente Sixto Villanueva, and Siy Ho, as sureties, executed a bond in favor of The Standard Oil Company of New York for ₱3,305.76, payable in three months, with interest at ₱1 per month.
The obligation was joint and several, binding each signatory to the full amount.

On April 5, 1909, the plaintiff sued all five obligors for the principal, interest from December 15, 1908, and costs.
Summons was served on Villanueva on April 17, 1909; on May 12, 1909, Villanueva and Siy Ho were declared in default (notices dated May 14 and 15).
On August 28, 1909, the Court of First Instance, Manila, rendered judgment against all defendants for ₱3,305.76, plus interest at 1% per month from December 15, 1908, until full payment, and costs.

While execution was pending, Elisa Torres de Villanueva, his wife, appeared alleging that on July 24, 1909, Vicente Sixto Villanueva had been judicially declared insane and she appointed guardian.
On October 11, 1909, the court authorized her to annul bonds executed during his alleged insanity, including the present bond.
She petitioned to vacate the judgment, reopen the trial, and introduce evidence of his incapacity at the time of the bond’s execution.
The court reopened the trial, heard medical and lay witnesses, found that Villanueva understood the bond on December 15, 1908, and was competent; it denied an indefinite stay and ordered execution to proceed.

Villanueva excepted to the trial court’s finding that monomania of wealth does not imply incapacity.
He appealed on the sole assignment that the lower court erred in holding his monomania did not void his capacity to execute the bond.

Does monomania of wealth, without more, constitute legal incapacity to execute a bond?
Was there sufficient proof that Villanueva was insane or lacked contractual capacity on December 15, 1908, when he executed the bond?