By the experience of active love. Strive to love your neighbour actively and indefatigably. In as far as you advance in love you will grow surer of the reality of God and of the immortality of your soul. If you attain to perfect self-forgetfulness in the love of your neighbour, then you will believe without doubt, and no doubt can possibly enter your soul. This has been tried. This is certain.
Fyodor Dostoevsky.. But do you understand, I cry to him, do you understand that along with happiness, in the exact same way, in perfectly equal proportion, man also needs unhappiness
Fyodor Dostoevsky