Leonard Nimoy was best known for the logical half human, half Vulcan character Mr. Spock. Spock supposedly strove for perfect logic, with no emotion affecting how he thought or acted.
I love logic. Logic is needed to separate truth from falsehood. A society that has no use for logic has no chance to live long and prosper. But pure logic is not sufficient for intelligent life.
In fact, if the only mental process is logic, no actions would ever be taken, because there would be no reasoning that could lead to action.
If you do not believe this, try using pure logic to prove why you should bother to continue living. You will find that you cannot do that without having some sort of starting point, some premise to start the chain of reasoning. One of the first great works of logic is Euclid's Elements, which summarizes ancient Greek knowledge of geometry. Euclid includes many proofs of geometric theorems, but he cannot prove anything without an initial set of definitions and axioms.
So what are the axioms for proving we should continue to live? Evolution has resulted in humans having emotions, and one of those is valuing our life. Emotions are the key to humanity, since emotions provide us with the reasons for what we do.
A problem with human nature is that the forces of evolution have not bothered to produce a set of emotions that are logically consistent or that will guide us to happiness. A person might desire to lose weight for health or social attractiveness, but that same person might desire to eat chocolate sundaes. Both desires cannot be fully satisfied, they are in logical conflict.
Maybe these conflicts in emotions give us a starting point to look at the role of logic in human life. Logic will enable us to recognize the conflicts in our emotions. Once recognized, maybe we can make a conscious choice of how to deal with the conflicts and prioritize our emotions.
The character of Mr. Spock demonstrated emotions that guided his actions. First, he did value his own life, since normally he took care of his health and safety. He was altruistic, often acting to promote the welfare of society or even alien species. He was curious, always seeking for scientific knowledge. When there was a conflict between these basic premises, such as a conflict between the desire to live and the desire for altruism, he logically recognized the conflict and consciously chose his priorities.
Human nature is what it is, and humans need emotions to motivate actions. But we can use logic to learn about our emotions, to teach ourselves to recognize the conflicts in our emotions and to consciously choose how to resolve the conflicts in a way that will make human life better.