The condition referred to as ‘mental assent’ happens when one tries to act as if they are in faith when they are really still in hope. Hope comes before faith.
Now faith is the substance of things hoped for, the evidence of things not seen. Hebrews 11:1
As you see the above verse – faith is (present tense) the substance of things hoped for (past tense). Faith is the substance of things already hoped for. Hope is wonderful and necessary but it is not faith. Hope knows that it may receive something, but faith knows that it will receive something. In fact, faith has already received it.
Hope comes primarily from reading the word of God. Faith comes by hearing the word of God by the Holy Spirit. It is the witness by God to the heart that you now have your hoped desire. It comes when you seek Him and hear Him. Faith is that which brings your hopes into reality.
For whatever was written in earlier times was written for our instruction, so that through perseverance and the encouragement of the Scriptures we might have hope. Romans 15:4
Faith comes by hearing, and hearing by the (spoken) word of God (Christ). Romans 10:17
Hope is primarily in the mind. Faith is primarily in the heart. ‘Mental ascent’ happens when the hopeful mind thinks that it is a believing heart. You know when you are in faith and you know when you are not in faith. Your heart knows and your mind should know. After you have been in faith, you will be able to tell the difference. Faith is based on hearing God and knowing that you know that you know. It is a knowing at your deepest level.
Once we have faith we have authority, we have ownership, and we can release that faith into the world. Once you have faith in your heart, you can release it in power-filled prayer.
Therefore, I say unto you, Whatsoever things you desire, when you pray, believe that you receive them and you shall have them. Mark 11:24