Infants and Reason

Since this is about faith only, we should study infants from that stand point. Catholics, including Luther, taught infants were saved in baptism without reason, and that faith was added later and continued to be the cause of salvation. Faith only was not applied to infants.

Pelagius would have used "faith only" for older after believers baptism.

Faith only was therefore a doctrine, when applied, for those of reason.

Catholics argued incorrectly the word children in Luke 18:15 meant infants in all cases. The catholic argument being (bringing children to be touched and blessed was equal to baptism, but it seems Jesus touched them and blessed them before their baptism), yet it says touch them. There is no reason to connect this to baptism. The passage has little relevance to baptism except in describing the word. Yes Jesus blessed young children with or without baptism.

So let's look at the word they always translate infant, and see that it can be used of an educated child.

Luk 18:15  AndG1161 they broughtG4374 unto himG846 alsoG2532 infants,G1025 thatG2443 he would touchG680 them:G846 butG1161 when his disciplesG3101 sawG1492 it, they rebukedG2008 them.G846 

Though it can mean infant, it can be applied to any age of child, even those who know the scriptures.

2Ti 3:15  AndG2532 thatG3754 fromG575 a childG1025 thou hast knownG1492 theG3588 holyG2413 scriptures,G1121 which are ableG1410 to make thee wiseG4679 G4571 untoG1519 salvationG4991 throughG1223 faithG4102 whichG3588 is inG1722 ChristG5547 Jesus.G2424 

It can be used of children that know the scriptures.

They can make you wise unto salvation through faith. The scriptures must be applied with wisdom and faith to save.

So, we see of children 

wisdom

faith

in Christ

Since wisdom was required then faith only was not accurate, it requires faith with a degree of reason and maturity.

Let's consider again the usage of the word child or children. Matthew, as Catholics teach,  gives the same account as Luke but uses a different word. Catholics might argue Luke used infant whereas Matthew used child or children. We have shown above the word used by Luke could be used of those knowing scripture.

Mat 18:5  AndG2532 whosoG3739 G1437 shall receiveG1209 oneG1520 suchG5108 little childG3813 inG1909 myG3450 nameG3686 receivethG1209 me.G1691 

Mat 18:6  ButG1161 whosoG3739 G302 shall offendG4624 oneG1520 of theseG5130 little onesG3398 which believeG4100 inG1519 me,G1691 it were betterG4851 for himG846 thatG2443 a millstoneG3458 G3684 were hangedG2910 aboutG1909 hisG846 neck,G5137 andG2532 that he were drownedG2670 inG1722 theG3588 depthG3989 of theG3588 sea.G2281 

Though the word can mean from infancy, it can also be a child with faith. "One of these little ones that believes in me." The Luke account doesn't seem to imply infants but children. Catholics simply translate it infant for doctrinal support.

We know that a child can have faith.

So that early christians speaking of children being baptized or being saved may not have meant infants at all.

Justin Martyr

"And both men and women who have been Christ's disciples since infancy, remain pure, and at the age of sixty or seventy years ..." (Justin Martyr, First Apology,15:6 -- AD 110-165)

Justin used infants/children as disciples. Those who translated his works could have translated it childhood vs infancy.

Thus the problem is in the translation, Catholics would translate the word infant because it would seem to support infant baptism. The word could easily be children, as if old enough to reason. It could even be the age of reading.

Here is a Catholic Article with imprimatur agreeing the account in Matthew and Luke are the same.

Although Fundamentalists are the most recent critics of infant baptism, opposition to infant baptism is not a new phenomenon. In the Middle Ages, some groups developed that rejected infant baptism, e.g., the Waldenses and Catharists. Later, the Anabaptists ("re-baptizers") echoed them, claiming that infants are incapable of being baptized validly. But the historic Christian Church has always held that Christ’s law applies to infants as well as adults, for Jesus said that no one can enter heaven unless he has been born again of water and the Holy Spirit (John 3:5). His words can be taken to apply to anyone capable of belonging to his kingdom. He asserted such even for children: "Let the children come to me, and do not hinder them; for to such belongs the kingdom of heaven" (Matt. 19:14). 

More detail is given in Luke’s account of this event, which reads: "Now they were bringing even infants to him that he might touch them; and when the disciples saw it, they rebuked them. But Jesus called them to him, saying, ‘Let the children come to me, and do not hinder them; for to such belongs the kingdom of God’" (Luke 18:15–16). 

http://www.catholic.com/tracts/infant-baptism

They leave out,

Mat 18:6  But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea. 

 As with household baptism such as Acts 10, they leave out certain parts.

Act 10:2  A devout man, and one that feared God with all his house, which gave much alms to the people, and prayed to God alway. 

They were old enough to fear.