Sheer void as belief
The purpose of the whole life (its goal) is necessarily associated with a belief as it is apprehended only after death (see elsewhere).
But what if I say that my belief about the end of life is sheer void? What if life has nothing afterwards, nothing tangible after death?
To address this, let us first make an important remark following general logical considerations.
Remark 1: The necessity of belief associated with the end of life does not equate to having any belief about what comes after death. This condition, being defined broadly, does not stipulate presence of inconsistent or wrongly posited beliefs. So beliefs, although a must in this context, have to be properly defined.
Void after death, no goal of life
If we assume absolute emptiness and sheer void after death, we have to necessarily conclude that the goals to be measured up against do not exist either: Nothing means nothing.
No result of the activity of life can be anticipated with such a belief. Therefore, this activity becomes without a goal. Any activity without a goal cannot be called rational.
Test 1: slap in the face
Imagine now a person confronting you and telling you that they are believers in sheer void after life. Imagine, too, that you could slap such a person in the face. What would their reaction be?
Will they respond, for example, in the form of a counter slap or a curse on your name, or a suit in the court of law?
Any similar-in-kind reaction prompted by the slap would indicate a liar. Indeed, if they truly believed in sheer void, nothing in this life would ever be appealing to them, since they would know an ultimate destroyer of everything of this life, death. They value this life or something in it, which is altogether inconsistent with the belief in sheer void.
Conclusion 2: The true belief in Sheer Void after death, although irrational (see Conclusion 1), sometimes may delude. In this case, if an individual under the delusion values anything or anybody of this life, they behave irrational (hence, they are doubly irrational in the light of Conclusion 1).
Another type of reaction prompted by the slap can be submission: the subject of your experiment submits himself to the pain and humiliation of the ego, he has no reaction to the aggressor, no bad feelings at all. He lives completely up to the understanding of the problem of death. But… he has no strength to finish a joke we call life (this is the solution of "weakness" according to Leo Tolstoy).
Their misery is understandable, the absurd of their position is inevitable.
Remark 2: There is very little of black-and-white in matters of belief. For example, people believing in God commit crimes in sheer contradiction to the divine law. Here, we enter the realm of compassion and empathy, rather than logical or empirical. We are not machines and we are weak too… However, the arguments of this essay concern mainly people pertaining to ardent opposition of anything believable or going beyond this life, people who deem themselves super-rational at times and those opposite them not rational at all…
Test 2: inheritance law
One of the greatest minds in the history of humanity, Al-Ghazali, gives the following example.
When faced with the question of life and its purpose, people promptly refer to the greatest of the great: the Ancient Greeks, Romans, Renaissance, Humanism, Absolutism, Relativism, Rationalism, Empiricism, Positivism, Darwinism at last. Well, even they have not concluded anything positive about anything after life, we can but follow the great minds of humanity.
However, when an ignorant peasant is deprived of inheritance by his own father and told to believe that his closest next of kin made a will to give all his possession to an unknown person, this peasant seeks the proof: what did his father write in the will? who were the witnesses? who was the solicitor? had the solicitor enough expertise (maybe, even asking another solicitor to double-check)? how much was granted to that third person? how much did his father have?
But why? This very peasant a minute ago was "stoically" defending the Ancient Greeks' position on the afterlife?
The answer is very simple. When you are not interested, when something does not concern you or worse it hampers anything that attracts you, you invent excuses, you make irrelevant queries and make prompt inconsistent conclusions. In other words, you renounce your own intellect. (Al-Ghazali does not even consider the Sheer Void as an intellectually valid position due to its foundations in desires.)
Example 1: A counter-example for the earlier peasant could be a highly educated intellectual (e.g., PhD, MD, and MBA in one person) pondering on the meaning of life with a glass of Romanée-Conti and a piece of Epoisses de Bourgogne, reciting effortlessly here and there from Stoics, Plato, Nietzsche, and Schopenhauer. Desires afflict everyone.