A personal stake in the outcome of the controversy which:

• Assures the concrete adverseness
• Sharoens the presentation of the issues
• Illuminates the court for difficult constitutional questions
• (Memory aid: concrete sharp bulb)

When a party has “alleged such a personal stake in the outcome of the controversy as to assure that concrete adverseness which sharpens the presentation of issues upon which the court so largely depends for illumination of difficult constitutional questions.” (Baker v. Carr) – Kilosbayan vs. Morato

The right of appearance in a court of justice on a given question. As a general rule, a party is not permitted to raise a matter in which he has no personal interest. – Ruling on the case against Anti-Terrorism Act of 2020 / Calleja vs. Executive Secretary (December 2021)