“This faith is different in degrees, weak or strong; may often and many ways assailed, and weakened, but gets the victory: growing up in many to the attainment of a full assurance, through Christ, who is both the author and finisher of our faith” (XIV.3).
Once again, let us weigh the claims of the WCF in the balances of Scripture and see if they are not found wanting:
“And being not weak in faith, he considered not his own body now dead, when he was about an hundred years old, neither yet the deadness of Sara’s womb: He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God” (Romans 4:19-20).
If Abraham HAD been weak in faith, He WOULD HAVE considered his own body now dead, and he WOULD HAVE staggered at the promise of God through UNBELIEF. And thus, he WOULD HAVE been weak in faith, not giving glory to God. What’s the conclusion drawn here? To be WEAK IN FAITH is to STAGGER THROUGH UNBELIEF.
“Wherefore, if God so clothe the grass of the field, which to day is, and to morrow is cast into the oven, shall he not much more clothe you, O ye of little faith?” (Matthew 6:30)
If someone says: “I doubt, that is, I’m not absolutely sure God will clothe me,” then it is clear that they have no faith in that provision.
The phrase “little faith” seems to be some type of euphemistic expression or figure of speech that is meant to convey that the person does not have faith at all since they do not believe that things such as provision of clothing will happen.
“And, behold, there arose a great tempest in the sea, insomuch that the ship was covered with the waves: but he was asleep. And his disciples came to him, and awoke him, saying, Lord, save us: we perish. And he saith unto them, Why are ye fearful, O ye of little faith? Then he arose, and rebuked the winds and the sea; and there was a great calm. But the men marvelled, saying, What manner of man is this, that even the winds and the sea obey him!” (Matthew 8:24-27)
“And he said unto them, Why are ye so fearful? how is it that ye have no faith? And they feared exceedingly, and said one to another, What manner of man is this, that even the wind and the sea obey him?” (Mark 4:40-41)
The figure of speech, “little faith” conveys the literal truth of having “no faith” as shown in comparing the two passages (Matthew 8:24-27; Mark 4:40-41) above. Those who knew not what manner of man this was that even the wind and the sea obey Him knew not the deity of Christ–they were of “little faith,” which is to say they had no faith concerning the truth of His deity.
“And the apostles said unto the Lord, Increase our faith. And the Lord said, If ye had faith as a grain of mustard seed, ye might say unto this sycamine tree, Be thou plucked up by the root, and be thou planted in the sea; and it should obey you” (Luke 17:5-6).
Jesus repeatedly describes His disciples as having “little faith.” This time around, they petition the Lord to “increase [their] faith.” They thought that they had true faith and only had need of “increasing” it. Jesus’ response demonstrates that these particular disciples—these “little faiths”—actually had no faith in the particular matter (vs. 1-4) at all. They thought they had a very weakened faith, but Jesus plainly tells them that they had not so much faith as even a mustard seed. It was not a matter strong faith versus weak faith; but a matter of true faith versus no faith. To have “mustard seed faith” as shown by Jesus’ employment of hyperbole is to have a sure and certain confidence that what is expected to happen will happen. For more on this, see “Faith is Assurance.”
“Then came the disciples to Jesus apart, and said, Why could not we cast him out? And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you” (Matthew 17:19-20).
Jesus contrasts unbelief with faith as a grain of mustard seed that manifests itself in boldness, assurance, and confidence. Thus even the smallest and weakest faith possible has full assurance of hope (Hebrews 6:11-12; 10:22). Anything less than the mustard seed faith that is sure and certain of what it hopes for is unbelief.
This is not to say that there is not a true distinction between strong faith and weak faith. Romans 14 speaks of those with a weak faith. Here, the WCF is just giving us a little taste of their damnable heresy that true Christians can doubt their salvation. Further elucidation is seen in XVIII. 3-4.
It is enough to say that BOTH “strong faiths” and “weak faiths,” “great faiths” and “little faiths,” if they are genuine mustard seed faith, ALL have full assurance. The weak faith of Romans 14 does not confuse or confound its own works with the works of Christ as its only hope of salvation.
The latter part of Hebrews 11:1 explains that faith is a certainty of things that are not seen. This faith believes that God created the universe (Hebrews 11:3). This faith is NOT “different in degrees, weak or strong;” it is NOT “often and many ways assailed, and weakened;” it does NOT eventually in time grow up in true believers “to the attainment of a full assurance, through Christ” because this faith already begins assured through Christ!
Hebrews 11:6 says that without faith it is impossible to please God. It states further that one must believe that He is. To doubt whether or not He is, is NOT to believe that He is. There is no room here for any so-called “degrees of faith” whereby a person doubts that God is and then grows up to a supposed “attainment of a full assurance” (XIV. 3) that God is.
Weak faith does not doubt as seen in such verses as Hebrews 11:1-3, 6, 11, and 13. The Biblical teaching on weak faith is found in Romans 14 for example. A Christian with weak faith eats only vegetables due to a tender conscience who may be grieved by the meat (food) of others. In Matthew 21:21 Jesus says: “If you have faith and do NOT doubt” (emphasis mine), contrasting the clear antithesis between faith and doubt.