“Believe in the Lord Jesus…” (Acts 16:31).
Salvation involves a turning from sin and a turning to God through the Lord Jesus Christ.
Faith is not strictly a process of logic, although there is nothing illogical in it. Believing is reasonable but is not the product of reason alone. Many have come to Christ after an examination of the evidence.
On the other hand, faith is not strictly a process of the heart. The desire to experience forgiveness, the emotions of release, and the hope of eternal life are as real as anything else in this life. But, believing is not just a feeling.
To believe is to lean the whole weight of one’s being on the Lord Jesus Christ, to commit your future and all your days to Him.
When your parent built you that treehouse it was good of you to say you believed it would support your weight because the one who built it loved you. The strength of the trunk and diameter of the heavy branches could logically be shown to be able to hold you. You believed when you stepped off the ladder into the treehouse.