@middleEast Logic does not define truth - It establishes the pathway to the discovery / uncovering of truth.
Like the quote from the famous Michelangelo, "Every block of stone already has a statue inside of it, and it's the task of the sculptor to discover it". In reference to this quote, its "truth" that would be the statue that already exists within the stone, and "logic" that is the device or means that the sculptor would use to discover it.
As for universal objective way to act, the logical conclusion is that all deliberate actions are primarily motivated by subjective things (like desire, belief, preference etc).
If there's actually a universally objective way to act --- It would be non-deliberate behavior, like making a mistake, or doing something by accident or unconsciously.
But if you consider the bigger picture, its hard to say that any event is accidental. For all that you know, any action that was deemed an accident by one person, may have been the intention of another entity with extra privileges and abilities than the average human (like a deity, or a powerful demon). There's no way to tell for sure whether or not anything was caused by accident.
TLDR. The universally objective way to act, is to act unconsciously or accidentally. But there's no way to tell for certain whether or not anything is accident. Because what is perceived as accident by one person, could be the intention of another entity, like a supreme being in a transcendent realm of existence.