"Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones"

This quote by Arthur Conan Doyle is stressing the significance of learning useful realities and not losing time on worthless facts. He is suggesting that when we find out something new, we tend to forget something that we currently knew. This is why it is very important to concentrate on learning useful truths that can be used in our lives. He is also recommending that if we spend excessive time learning ineffective truths, we will end up forgetting the beneficial ones. This is why it is necessary to focus on finding out helpful realities over useless ones. By doing this, we can make sure that we are not losing our time and energy on facts that will not be beneficial to us in the long run.