No problem MarcR, maybe I'm misunderstanding Rom_10:9. But I don't see believing with your heart as being mental assent. Could you explain how a person believes with their heart?
Rom_10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
The word heart is not what we in the 21st century would think.
It has to do with the thoughts of the mind.
It often has to do with the baser passions plus the thoughts, its self.
In fact Jesus also said:
Mat 12:34 O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh.
Mat 12:35 A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things.
Mat 12:36 But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment.
Mat 12:37 For by thy words thou shalt be justified, and by thy words thou shalt be condemned.
notice the connection again with the words and the heart. In this next one Jesus is rebuking the elders for not keeping the commandments but rather their traditions.
Mat 15:3 But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?
Mat 15:4 For God commanded, saying, Honour thy father and mother: and, He that curseth father or mother, let him die the death.
Mat 15:5 But ye say, Whosoever shall say to his father or his mother, It is a gift, by whatsoever thou mightest be profited by me;
Mat 15:6 And honour not his father or his mother, he shall be free. Thus have ye made the commandment of God of none effect by your tradition.
Mat 15:7 Ye hypocrites, well did Esaias prophesy of you, saying,
Mat 15:8 This people draweth nigh unto me with their mouth, and honoureth me with their lips; but their heart is far from me.
Mat 15:9 But in vain they do worship me, teaching for doctrines the commandments of men.
So they confess Jesus with their mouth but their heart is far form Him. So simply having the words does not save there must be a heart conversion.
Mat 15:18 But those things which proceed out of the mouth come forth from the heart; and they defile the man.
Mat 15:19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
Mat 15:20 These are the things which defile a man: but to eat with unwashen hands defileth not a man.
Notice what comes out of the heart, evil thoughts, thoughts come from the mind the brain but we should be careful not to make this purely intellectual, while the intellectual is there it is affected by emotions, mood etc all that makes us who we are.
Luk 6:44 For every tree is known by his own fruit. For of thorns men do not gather figs, nor of a bramble bush gather they grapes.
Luk 6:45 A good man out of the good treasure of his heart bringeth forth that which is good; and an evil man out of the evil treasure of his heart bringeth forth that which is evil: for of the abundance of the heart his mouth speaketh.
Luk 6:46 And why call ye me, Lord, Lord, and do not the things which I say?
So it is clear that the heart involves the self which includes the intellect. This is how faith comes:
Rom 10:17 So then faith cometh by hearing, and hearing by the word of God.
For faith to come one must hear or read and the brain/intellect is most certainly involved in this process.