Updated: Aug 25, 2019
I doubt that truth is indeed the highest good. While truth by itself is a very important value in life, I believe there can be, at least for some portions of the population under some circumstances, other values which are important at some period of their lives, and are good for them even more than knowing the truth.
Take children, for example. If children would know every piece of truth they encounter in their early life - they may unnecessarily suffer because they may be not mentally immune to such truth, mostly truth with a dark tone:
"Where is Lucky? I can’t find her anywhere”
“Lucky got run over a truck while it was trying to run away from our home.”
This is a perfect example to a case which, for kids, the truth is wrong to be executed. The child, overwhelmed by the trauma of truth, may suffer very much for the next periods of his life, which may be, psychologically, more harsh on him… and all because he wasn’t deceived as a way to keep himself from harm’s way.
Children need to be deceived, because lying may serve them a purpose as a safety net that may assist them to raise their emotional immunity in the future. If truth would be indeed the highest good, it would’ve been worthy for all populations to be exposed to it - but is it worthy for a child to experience trauma because he was exposed to the truth about his dead dog?
What about government secrets? There are reasons for governments to hide their most secretive intelligence: at times, knowing so much can cause panic in the public, and therefore shaken the general order in a country. This is why the intimate truth is kept out of public reach - it may be dangerous for the general security. Again: if the truth was the highest good, everyone are worthy to know it - but is this sentence true when it comes to fragile information that even can put lives of many in danger?
Truth as the highest good, when in execution, means: everyone has the right to know each little information which is true. If so, then why governments hide secret information from their citizens, if not for their safety?
Here’s another example: An old man, who used to be a CEO of a large, successful corporation, in which he worked to so hard throughout his life in order to bring it into its highest of peaks and achievements - is about to die. What he does not know, is that one of the managers filled the chair he left, and brought the corporation into bankruptcy. Next to the former CEO bed sits one of his most loyal employees, who developed a very deep relationship with the CEO, like a relationship between a teacher and a follower.
Shortly before his death, the CEO asks his beloved employee: “How’s the corporation going? Is it in a good state?”
But… the corporation got bankrupt, and the man is about to die. If the truth were the highest good, the employee would have to tell the old man that the corporation he so dreamed of and worked so hard to bring it to success - does not exists anymore! Are old men and women need to spend their last living moments in worry and fear? No, they should die honorably with serenity, not with an anxiety attack. Therefore, even if the former employee would betray his boss and mentor, I believe a moral act to do is to tell him that the corporation is doing great, even if that would mean to deceive him in his last moments of living.
In conclusion: Truth may be a very valuable concept in life, but at times there may be much more higher values than it. Protection, safety and honor - those are just few examples to prove that truth is not the highest good.
Is there any highest good that can be applied to every situation on the universal aspect? Again, I highly doubt it, as different situations require different values as highest goods.