The following lengthy quotation comes from a volume from 1904 by Charles W. Penrose (1832-1925), an early 20th century LDS leader. It is a very good refutation of the relativism that is, alas, still alive today, where even Latter-day Saints have the attitude that it doesn’t really matter what people believe in as long as they are “good people” and/or “simply believe in Jesus”:
One of the great errors into which people have fallen in reference to religion is that God must accept any mode of worship, any sort of ordinances, and any kind of church that men may establish, so long as they are sincere in their intentions and devout in their desires. God must be worshipped not only in spirit but in truth. His word is truth. His Spirit is the spirit of truth. God's religion, then, will be the truth, and nothing but the truth, and he will accept of nothing short of this. The inventions of men, whatever may be their motives, are not of God and therefore are vain. The precepts and opinions and vagaries of man-appointed preachers and teachers, not being authorized or inspired of God, cannot be relied upon and are not acknowledged in heaven. Christendom as well as heathendom is in a ferment with human conceptions and conflicting theories in relation to God, his will, his purposes, and his requirements. The result is spiritual Babylon, which is confusion. God is not with it, for he is the author of peace, and order and harmony.
"Strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it;" so said the great Teacher whom professing Christians regard as the Savior of the world (Matthew 7:14). He also declared: "Verily, verily, I say unto you, He that entereth not by the door into the sheep-fold, but climbeth up some other way, the same is a thief and a robber" (John 10:1). Also, "But in vain they do worship me, teaching for doctrines the commandments of men" (Matthew 15:9). And further, "Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God" (Matthew 4:4).
The nations that are called heathen are, no doubt, as sincere in their idolatrous worship as are the Christian nations in their opposing creeds and devotional exercises. If mere sincerity and devout motives are sufficient for God's acceptance, then heathendom is on a par with Christendom in the sight of heaven. But the objector will no doubt reply, "Heathen religions lack the one essential feature of acceptance with God, faith in Jesus Christ. Having that, doctrinal differences do not matter; faith alone is sufficient for salvation." "Christ is the way, the truth, and the light, and whosoever believeth in him shall have eternal life." That is another of the astonishing errors of modern religious people and teachers. Seizing upon a few isolated texts from the New Testament, relying upon the letter of the word alone, regardless of the spirit and meaning thereof, they altogether ignore numerous other texts in the same volume, which make plain the intent and signification of those which they select. Their eyes are blinded to the pure truth, they stumble in the way, and the blind leading the blind, they are in danger of falling into the ditch together.
Jesus of Nazareth truly said, "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life" (John 3:16). But he also said, "My sheep hear my voice, and I know them, and they follow me" (John 10:27). "Verily, verily, I say unto you, He that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father" (John 14:12). "If a man love me, he will keep my words" (Verse 23). "He that hath my commandments, and keepeth them, he it is that loveth me; and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him." (Verse 21.) "If ye keep my commandments, ye shall abide in my love; even as I have kept my Father's commandments, and abide in his love." (John 15:10.) "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven." (Matthew 7:21.) "And why call ye me, Lord, Lord, and do not the things which I say?" (Luke 6:46.) "Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven. For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven." (Matthew 5:19-20.) "And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand: and the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it." (Matthew 7:26, 27.) "Every tree that bringeth not forth good fruit is hewn down, and cast into the fire. Wherefore by their fruits ye shall know them." (Matthew 7:19.) When the rich young man asked the Savior what he should do that he might have eternal life, he was not told there was nothing for him to do but believe in Christ, but the answer was, "If thou wilt enter into life, keep the commandments." (Matthew 19:17.) After Christ's resurrection, when he sent his apostles into all the world to preach the gospel to every creature, he added, "Teaching them to observe all things whatsoever I have commanded you." (Matthew 28:20.)
The apostles, thus authorized, obeyed these instructions, and not only proclaimed belief in Jesus Christ as necessary to salvation; but obedience to his teachings as equally essential. The history of their travels, as narrated in the book called the Acts of the Apostles, demonstrates this to be true. Such of their epistles as have been preserved and compiled in the New Testament also bear this witness. These records show beyond reasonable dispute that the faith in Christ which is sufficient for salvation comprehends faith in his teachings and obedience to his commands.
The belief in Christ which is taught by modern Christian sects is thus condemned by the Apostle James: "But wilt thou know, O vain man, that faith without works is dead? Ye see then how that by works a man is justified, and not by faith only." "For as the body without the spirit is dead, so faith without works is dead also" (James 2:20, 24, 26). (Charles William Penrose, Rays of Living Light on the One Way of Salvation [Salt Lake City: The Deseret News, 1904; repr., Forgotten Books, 2015], 4-7 [an online version of the book can be found here])
