To the degree that a life with meaning and purpose has value, it has the same type of value as anything else in the universe might have. It has value in virtue of being such as to fulfill the desires in question. If those desires are absent, then it has no value.
This creates something of a problem.
I have been writing this series of postings as if to say meaning and purpose do not exist. A person who has a desire for a life of meaning and purpose is in the same condition as somebody who has a desire to serve God or to have been born of another species. It is a desire that can never be fulfilled.
There are, however, several options. The option we choose depends on a number of relevant facts, which includes facts about convenience.
This is because we are not talking about choosing what is true about the universe, but choosing how we talk about the universe.
It is not enough to say that P, for some desire that P, is not real and the desire is a waste. Desires are persistent entities. The discovery that a desire is not now (and never will be) fulfilled will not cause the desire to simply vanish. The desire will remain, causing the agent who believes that its fulfillment is impossible.
It would be great if the recognition that a pain cannot be extinguished would be sufficient to cause the aversion to pain to vanish, but we do not live in such a universe.
This particularly strong desire for a life of meaning and purpose leaves those who have it vulnerable to charlatans and metaphysical snake-oil salesmen who claim to know a rout to this meaning and purpose. They lie, selling something that does not exist to people whose suffering is relieved, in part, by the belief that it exists even though the belief is false.
They are like con-artists who claim that can speak to the dead and can give a person with a desire to do so a chance to speak to some departed relative, or those who claim that if they (the con-artist) is obeyed the victim will get eternal life.
The trap has been sprung. A few people have a chance to escape by recognizing how a desire to learn and understand, a desire to care for one's children, a desire to teach, and the like has the same type of value as a desire for meaning and purpose.
However, the vast majority of people will read the claim that a desire for a life of meaning and fulfillment will never exist as a source of despair, even (suicidal) agony. All because they have been caused to have a desire that P in a universe in which P can never be made or kept true.
One alternative that handles this problem would be to turn 'purpose' and ‘meaning’ into synonyms for 'value'. To claim that a state (or the act of realizing a state) gives one's life purpose and meaning would make a type of sense. A person seeking purpose and meaning would, in this sense, be a person attempting to discover what states are such as to fulfill his or her desires.
However, if we select this option we would have to change how we speak about meaning and purpose. Hitler's life had meaning in this sense – in that found a sense of purpose in eliminating the Jews. In this sense, a person speaking about having discovered meaning and purpose could not be taken as having discovered anything of value. The rest of us might have good reason to shrug our shoulders and ask, "So?" Or, worse, the rest of us might have many and good reasons to condemn anybody who would find purpose in a state such as exterminating the Jews or becoming a member of the slave-owning aristocracy.
These are the types of choices one fails any time when one adopts an 'error theory'. There are multiple ways to resolve the error, but none of them would be fully satisfactory. There is no answer that fully captures 'traditional uses' since that traditional use contains the error we are seeking to eliminate.