LBC 1; Paragraph 6. The whole counsel of God concerning all things necessary for His own glory, man's salvation, faith and life, is either expressly set down or necessarily contained in the Holy Scripture: unto which nothing at any time is to be added, whether by new revelation of the Spirit, or traditions of men.9 Nevertheless, we acknowledge the inward illumination of the Spirit of God to be necessary for the saving understanding of such things as are revealed in the Word,10 and that there are some circumstances concerning the worship of God, and government of the church, common to human actions and societies, which are to be ordered by the light of nature and Christian prudence, according to the general rules of the Word, which are always to be observed.
The debate over intinction, and grape juice, and leaven in regards to the Supper seems to distill down to this one question: What things are 'expressly set down or necessarily contained in the Holy Scripture' and what things are 'circumstances which are ordered by the light of nature and Christian prudence'?
If the Scriptures, either expressly or by good and necessary consequence, teach that wine is to be used then wine it must be. If the Scriptures do not, either expressly or by good and necessary consequence, teach that wine is to be used then the liquid is to be determined by the light of nature and Christian prudence.
The same could be said for leavened or unleavened bread, or for the combining of the wine and the bread into a new substance prior to partaking, or for the frequency of participation.
I would like to hear arguments either way in regards to elements and circumstances in the Lord's Supper.