Do Not Become the Culture To Win The Culture - John McArthur 

Fantastic question - I hope this helps: Jesus said, in Matthew 12:34 is - "O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh." According to Jesus, you can't just talk a good game and then live however you like. What's in a persons deepest held thoughts will eventually be 'betrayed' by their mouth. The mouth is represented here as the sort of 'amplifier' for that which we personally, deep down, hold dear - the inner philosophy which individually defines each of us.. There's a saying in Latin: "Qualis vir talis oratio", meaning "The way a man speaks reveals his character". What you think.. is what you eventually say. This is how man is wired. This is one of the great gauges which let us know where we stand on spiritual things. Does what we think and SAY line up with scripture? - - Psalms 141: 3 - and the first part of 4 - "Set a watch, O Lord, before my mouth; keep the door of my lips. 4: Incline not my heart to any evil thing." (See how closely scripture relates the heart and the mouth?) What we say is one of the best ways to gauge where we stand in our walk with God. "The heart is deceitful, and desperately wicked above all things, and who can know it?" Jer. 17:9. The heart, being the seat of mankind's personal philosophy... this is the philosophy we are born with.. but, according to scripture, one which does not work for us (hence the need for a Savior). When we come into the world, our own 'natural' philosophy SEEMS right to us (But, as scripture points out, this philosophy is counter to God's philosophy - The Word). Prov. 16:25 - There is a way that *seemeth* right unto a man, but the end thereof are the ways of death. It SEEMS right to want to get back at those who use us poorly. It SEEMS right to want to hoard our resources. It SEEMS right to take an eye for an eye. It SEEMS right to preserve our lives at all cost. This is the way of the 'natural' man. But in the realm of the Kingdom of God, everything is backwards for the Spiritual Man. In the spiritual realm (not the natural) We 'give to get'.. .we 'lay down our lives to save them'.. we 'pray for those who despitefully use us'. This is why scripture admonishes us to "Let this Mind - (This Thought process.. or This philosophy) - be in you .. which was also in Christ Jesus" - Philippians 2:5. Jesus WAS The Word - in human form. Likewise, WE are to become The Word in human form. And this is why we "Study, to show ourselves approved" - 2nd Timothy 21:15. "Wherewithal shall a young man cleanse his way? By taking heed thereto according to THY WORD". The Word of God... the mind of God ..the Essence of God.. the Spirit of God.. the philosophy of God.. All one and the same. The Word. God's philosophy, and not our own. This is what we eat. This is the disciples' diet - the Word and Mind of God...and this is what we hide in our souls.. .so that when it's time to speak... OUT comes The Word.. and not what was originally in our hearts at birth. God gives us a chance at redemption and says, very simply ... "I'm going to give you a chance .. to exchange the sin nature you were born with .. the philosophy In Your Heart, which Does Not, and Cannot, work for you .. for My Own philosophy - My Word (Jesus, according to John 1:1), which works 100% of the time." - So to answer the question ... The only way we can truly trust what comes out of our mouth... is when we are speaking the Word of God over every situation in our lives... rather than our own philosophy, which as scripture says... just cannot work for us, and eventually leads to destruction. So, In this way, the two references actually compliment one another. I hope that's helpful.