This excerpt is taken in whole from ‘The Institutes of the Christian Religion’ by John Calvin.

6. By person, then, I mean a subsistence in the Divine essence – a subsistence which, while related to the other two, is distinguished from them by incommunicable properties.  By subsistence we wish something else to be understood than essence.  For if the Word were God simply, and had not some property peculiar to himself, John could not have said correctly that he had always been with God.  When he adds immediately after, that the Word was God, he calls us back to the one essence.  But because he could not be with God without dwelling in the Father, hence arises that subsistence, which, though connected with the essence by an indissoluble tie, being incapable of separation, yet has a special mark by which it is distinguished from it.  Now, I say that each of the three subsistences while related to the others, is distinguished by its own properties.  Here relation is distinctly expressed, because, when God is mentioned simply and indefinitely, the name belongs not less to the Son and Spirit than to the Father.  But whenever the Father is compared with the Son, the peculiar property of each distinguishes the one from the other.  Again, whatever is proper to each I affirm to be incommunicable, because nothing can apply or be transferred to the Son which is attributed to the Father  s a mark of distinction.  I have no objection to adopt the definition of Tertullian, provided it is properly understood, ‘that there is in God a certain arrangement or economy, which makes no change on the unit of the essence’ (Tert. Lib. Contra Praeam).

7. Before proceeding farther, it will be necessary to prove the Divinity of the Son and the Holy Spirit.  Thereafter, we shall see how they differ from each other.  When the Word of God is set before us in the Scriptures, it were certainly most absurd to imagine that it is only a fleeting and evanescent  voice, which is sent out into the air, and comes forth beyond God himself, as was the case with the communications made to the patriarchs, and all the prophecies.  The reference is rather to the wisdom ever dwelling with God, and by which all oracles and prophecies were inspired.  For, as Peter testifies (1 Pet 1:11), the ancient prophets spake by the Spirit of Christ just as did the apostles, and all who after them were ministers of the heavenly doctrine.  But as Christ was not yet manifested, we necessarily understand that the Word was begotten of the Father before all ages.  But if that Spirit, whose organs the prophets were, belonged to the Word, the inference is irresistible, that the Word was truly God.  And this is clearly enough shown by Moses in his account of the creation, where he places the Word as intermediate.  For why does he distinctly narrate that God, in creating each of his works, said, Let there be this – let there be that, unless the unsearchable glory of God might shine forth in his image?  I know prattlers would easily evade this, by saying that the Word is used for order or command; but the apostles are better expositors, when they tell us that the worlds were created by the Son, and that he sustains all things by his mighty word (Heb 1:2).  For we see here that word is used for the nod or command of the Son, who is himself the eternal and essential Word of the Father.  And no man of sane mind can have any doubt as to Solomon’s meaning, when he introduces Wisdom as begotten by God, and presiding at the creation of the world, and all other divine operations (Prov 8:22).  For it were trifling and foolish to imagine any temporary command at a time when God was pleased to execute his fixed and eternal counsel, and something more still mysterious.  To this our Saviour’s words refer, ‘My Father worketh hitherto, and I work’ (Jn 5:17).  In thus affirming, that, from the foundation of the world he constantly worked with the Father, he gives a clearer explanation of what Moses simply touched.  The meaning therefore is, that God spoke in such a manner as left the Word his peculiar part in the work, and thus made the operation common to both.  But the explanation is given by John, when he states that the Word which was from the beginning, God and with God, was, together with God the Father, the maker of all things.  For he both attributes a substantial and permanent essence to the Word, assigning to it a certain peculiarity, and distinctly showing how God spoke the world into being.  Therefore, as all revelations from heaven are duly designated by the title the Word of God, so the highest place must be assigned to that substantial Word, the source of all inspiration, which, as being liable to no variation, remains forever one and the same with God, and is God.

8. Here an outcry is made by certain men, who, while they dare not openly deny his divinity, secretly rob him of his eternity.  For they contend that the Word only began to be when God opened his sacred mouth in the creation of the world.  Thus, with excessive temerity, they imagine some change in the essence of God.  For as the names of God, which have respect to external work, began to be ascribed to him from the existence of the work (as when he is called the Creator of heaven and earth), so piety does not recognise or admit any name  which might indicate that a change had taken place in God himself.  For if anything adventitious took place, the saying of James would cease to be true, that ‘every good gift, and every perfect gift, is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning (James 1:17).  Nothing, therefore, is more intolerable than to fancy a beginning to that Word which was always God, and afterwards was the Creator of the world.  But they think they argue acutely, in maintaining that Moses, when he says that God then spoke for the first time, must be held to intimate that till then no Word existed in him.  This is the merest trifling.  It does not surely follow, that because a thing begins to be manifested at a certain time, it never existed previously.  I draw a very different conclusion.  Since at the very moment when God said, ‘Let there be light’, the energy of the Word was immediately exerted, it must have existed long before.  If any enquire how long, he will find it was without beginning.  No certain long period of time is defined, when he himself says, ‘Now, O Father, glorify thou me with thine own self, with the glory which I had with thee before the world was’ (John 17:5).  Nor is this omitted by John: for before he descends to the creation of the world, he says that, ‘in the beginning was the Word, and the Word was with God’.  We, therefore, again conclude, that the Word was eternally begotten by God, and dwelt with him from everlasting.  In this way, his true essence, his eternity, and divinity, are established.

9. But though I am not now treating of the office of the Mediator having deferred it till the subject of redemption is considered, yet because it ought to be clear and incontrovertible to all, that Christ is that Word become incarnate, this seems the most appropriate place to introduce those passages which assert the Divinity of Christ.  When it is said in the forty-fifth Psalm, ‘Thy throne, O God, is for ever and ever’, the Jews quibble that the name Elohim is applied to angels and sovereign powers,  But no passage is to be found in Scripture, where an eternal throne is set up for a creature.  For he is not called God simply, but also the eternal Ruler.  Besides, the title is not conferred on any man, without some addition, as when it is said that Moses would be a God to Pharaoh (Exod 7:1).  Some read as if it were in the genitive case, but this is too insipid.  I admit, that anything possessed of singular excellence is often called divine, but it is clear from the context, that this meaning here were harsh and forced, and totally inapplicable.  But if their perverseness still refuses to yield, surely there is no obscurity in Isaiah, where Christ is introduced both as God, and as possessed of supreme power, one of the peculiar attributes of God, ‘His name shall be called the Mighty God, the Everlasting Father, the Prince of Peace’ (Isa 9:6).  Here, too, the Jews object, and invert the passage thus, This is the name by which the Mighty God, the Everlasting Father, will call him; so that all which they leave the Son is, ‘Prince of Peace’.  But why should so many epithets be here accumulated on God the Father, seeing the prophet’s design is to present the Messiah with certain distinguished properties which may induce us to put our faith in him?  There can be no doubt, therefore, that he who a little before was called Immanuel, is here called the Mighty God.  Moreover, there can be nothing clearer than the words of Jeremiah, ‘This is the name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS’ (Jer 23:6).  For as the Jews themselves teach that the other names of God are mere epithets, whereas this, which they call the ineffable name, is substantive, and expresses his essence, we infer, that the only begotten Son is the eternal God, who elsewhere declares, ‘My glory will I not give to another’ (Isa 42:8).  An attempt is made to evade this from the fact, that this name is given by Moses to the altar which he built, and by Ezekiel to the New Jerusalem.  But who sees not that the altar was erected as a memorial to show that God was the exalter of Moses, and that the name of God was applied to Jerusalem, merely to testify the Divine presence?  For thus the prophet speaks. ‘The name of the city from that day shall be, The Lord is there’ (Ezek 48:35).  In the same way, ‘Moses built an altar, and called the name of it JEHOVAH-nissi’ (Jehovah my exaltation).  But it would seem the point is still more keenly disputed as to another passage in Jeremiah, where the same title is applied to Jerusalem in these words, ‘In those days shall Judah be saved, and Jerusalem shall dwell safely; and this is the name whereby she shall be called, The Lord our Righteousness’.  But so far is this passage from being adverse to the truth which we defend, that it rather supports it.  The prophet having formerly declared that Christ is the true Jehovah from whom righteousness flows, now declares that the Church would be made so sensible of this as to be able to glory in assuming his very name.  In the former passage, therefore, the fountain and cause of righteousness is set down; in the latter, the effect is described.

10. But if this does not satisfy the Jews, I know not what cavils will enable them to evade the numerous passages in which Jehovah is said to have appeared in the form of an Angel (Judges 6, 7, 13:16-23 etc.).  This angel claims for himself the name of the Eternal God.  Should it be alleged that this is done in respect of the office which he bears, the difficulty is by no means solved.  No servant would rob God of his honour, by allowing sacrifice to be offered to himself.  But the Angel, by refusing to eat bread, orders the sacrifice due to Jehovah to be offered to him.  Thus the fact itself proves that he was truly Jehovah.  Accordingly, Manoah and his wife infer from the sign, that they had not only seen an angel, but God.  Hence Manoah’s exclamation, ‘We shall die; for we have seen the Lord’.  When the woman replies, ‘If Jehovah had wished to slay us, he would not have received the sacrifice at our hand’, she acknowledges that he who is previously called an angel was certainly God.  We may add, that the angel’s own reply removes all doubt, ‘Why do ye ask my name, which is wonderful?’  Hence the impiety of Servetus was the more detestable, when he maintained that God was never manifested to Abraham and the Patriarchs, but that an angel was worshipped in his stead.  The orthodox doctors of the Church have correctly and wisely expounded, that the Word of God was the supreme angel, who then began, as it were, by anticipation, to perform the office of Mediator.  For though he were not clothed with flesh, yet he descended as in an intermediate form, that he might have more familiar access to the faithful.  This closer intercourse procured for him the name of an Angel; still, however, he retained the character which justly belonged to him – that of the God of ineffable glory.  The same thing is intimated by Hosea, who, after mentioning the wrestling of God with the angel, says, ‘Even the Lord God of hosts; the Lord is his memorial’ (Hosea 12:5).  Servetus again insinuates that God personated an angel; as if the prophet did not confirm what had been said by Moses, ‘Wherefore is it that thou dost ask after my name?’ (Gen 32:29-30).  And the confession of the holy Patriarch sufficiently declares that he was not a created angel, but one in whom the fullness of the Godhead dwelt, when he says, ‘I have seen God face to face’.  Hence also Paul’s statement, that Christ led the people in the wilderness (1 Cor 10:4…).  Although the time of humiliation had not yet arrived, the eternal Word exhibited a type of the office which he was to fulfil.  Again, if the first chapter of Zechariah (verse 9 etc.) and the second (verse 3 etc.) be candidly considered, it will be seen that the angel who sends the other angel is immediately after declared to be the Lord of hosts, and that supreme power is ascribed to him.  I omit numberless passages in which our faith rests secure, though they may not have much weight with the Jews.  For when it is said in Isaiah, ‘Lo, this is our God; we have waited for him and he will save us: this is the Lord; we have waited for him, we will be glad and rejoice in his salvation’ (Isa 25:9), even the blind may see that the God referred to is he who again rises up for the deliverance of his people.  And the emphatic description, twice repeated, precludes the idea that reference is made to any other than to Christ.  Still clearer and stronger is the passage of Malachi, in which a promise is made that the messenger who was then expected would come to his own temple (Mal 3:1).  The temple certainly was dedicated to Almighty God only, and yet the prophet claims it for Christ.  Hence it follows, that he is the God who was always worshipped by the Jews. 

11. The New Testament teems with innumerable passages, and our object must therefore be, the selection of a few, rather than an accumulation of the whole.  But though the Apostles spoke of him after his appearance in the flesh as Mediator, every passage which I adduce will be sufficient to prove his eternal Godhead.  And the first thing deserving of special observation is, that predictions concerning the eternal God are applied to Christ, as either already fulfilled in him, or to be fulfilled at some future period.  Isaiah prophesies, that ‘the Lord of Hosts’ shall be ‘for a stone of stumbling, and for a rock of defence’ (Isa 8:14).  Paul asserts that this prophecy was fulfilled in Christ (Rom 9:33), and therefore declares that Christ is that Lord of Hosts.  In like manner, he says in another passage, ‘We shall all stand before the judgment seat of Christ.  For it is written, ‘As I live, saith the Lord, every knee shall bow to me, and every tongue confess to God’.  Since in Isaiah God predicts this of himself (Isa 45:23), and Christ exhibits the reality fulfilled in himself, it follows that he is the very God, whose glory cannot be given to another.  It is clear also, that the passage from the Psalms (Ps 68:19) which he quotes in the Epistle to the Ephesians, is applicable only to God, ‘When he ascended up on high, he led captivity captive’ (Eph 4:8).  Understanding that such an extension was shadowed forth when the Lord exerted his power, and gained a glorious victory over heathen nations, he intimates that what was thus shadowed was more fully manifested in Christ.  So John testifies that it was the glory of the Son which was revealed to Isaiah in a vision (John 12:41; Isa 6:4), though Isaiah himself expressly says that what he saw was the Majesty of God.  Again, there can be no doubt that those qualities which, in the Epistle to the Hebrews, are applied to the Son, are the brightest attributes of God, ‘Thou, Lord, in the beginning hast laid the foundation of the earth’, etc., and ‘Let all the angels of God worship him’ (Heb 1:10, 6).  And yet he does not pervert the passages in thus applying them to Christ, since Christ alone performed the things which these passages celebrate.  It was he who arose and pitied Zion – he who claimed for himself dominion over all nations and islands.  And why should John have hesitated to ascribe the Majesty of God to Christ, after saying in his preface that the Word was God? (Jn 1:14).  Why should Paul have feared to place Christ on the judgement-seat of God (2 Cor 5:10), after he had so openly proclaimed his divinity, when he said that he was God over all, blessed for ever?  And to show how consistent he is in this respect, he elsewhere says that ‘God was manifest in the flesh’ (1 Tim 3:16).  If he is God blessed for ever, he therefore it is to whom alone, as Paul affirms in another place, all glory and honour is due.  Paul does not disguise this, but openly exclaims, that ‘being in the form of God, (he) thought it not robbery to be equal with God, but made himself of no reputation’ (Phil 2:6).  And lest the wicked should clamour and say that he was a kind of spurious God, John goes farther, and affirms, ‘This is the true God, and eternal life’.  Though it ought to be enough for us that he is called God, especially by a witness who distinctly testifies that we have no more gods than one, Paul says, ‘Though there be that are called gods, whether in heaven or in earth (as there be gods many, and lords many), but to us there is but one God’ (1 Cor 8:5-6).  When we hear from the same lips that God was manifest in the flesh, that God purchased the Church with his own blood, why do we dream of any second God, to whom he makes not the least allusion?  And there is no room to doubt that all the godly entertained the same view.  Thomas, by addressing him as his Lord and God, certainly professes that he was the only God whom he had ever adored (John 20:28).

12. The divinity of Christ, if judged by the works which are ascribed to him in Scripture, become still more evident.  When he said of himself, ‘My Father worketh hitherto, and I work’, the Jews, though most dull in regard to his other sayings, perceived that he was laying claim to divine power.  And, therefore, as John relates (Jn 5:17), they sought to the more to kill him, because he not only broke the Sabbath, but also said that God was his Father, making himself equal with God.  What, then, will be our stupidity if we do not perceive from the same passage that his divinity is plainly instructed?  To govern the world by his own power and providence, and regulate all things by an energy inherent in himself, (this an Apostle ascribes to him, Heb 1:3), surely belongs to none but e Creator.  Nor does he merely share the government of the world with the Father, but also each of the other offices, which cannot be communicated to creatures.  The Lord proclaimed by his prophet, ‘I, even I, am he that blotteth out thy transgressions for mine own sake’ (Isa 43:25).  When, in accordance with this declaration, the Jews thought that injustice was done to God when Christ forgave sins, he not only asserted, in distinct terms, that his power belonged to him, but also proved it by a miracle (Matt 9:6).  We thus see that he possessed in himself not the ministry of forgiving sins, but the inherent power which the Lord declares he will not give to another.  What!  Is it not the province of God alone to penetrate and interrogate the secret thoughts of the heart?  But Christ also had this power, and therefore we infer that Christ is God.

13. How clearly and transparently does this appear in his miracles?  I admit that similar and equal miracles were performed by the prophets and apostles; but there is this very essential difference, that they dispensed the gifts of God as his ministers, whereas he exerted his own inherent might.  Sometimes, indeed, he used prayer, that he might ascribe glory to the Father, but we see that for the most part his own proper power was displayed.  And how should he not be the true author of miracles, who, of his own authority, commissions others to perform them?  For the evangelist relates that he gave power to the apostles to cast out devils, cure the lepers, raise the dead, etc.  And they, by the mode in which they performed this ministry, showed plainly that their whole power was derived from Christ.  ‘In the name of Jesus Christ of Nazareth’, says Peter (Acts 3:6), ‘rise up and walk’.  It is not surprising, then, that Christ appealed to his miracles in order to subdue the unbelief of the Jews, inasmuch as these were performed by his own energy, and theretofore bore the most ample testimony to his divinity.

Again, if out of God there is no salvation, no righteousness, no life, Christ, having all these in himself, is certainly God.  Let no one object that life or salvation is transfused into him by God.  For it is said not that he has received, but that he himself is salvation.  And if there is none good but God, how could a mere man be pure, how could he be, I say not good and just, but goodness and justice?  Then what shall we say to the testimony of the evangelist, that from the very beginning of the creation ‘in him was life, and this life was the light of men’?  Trusting to such proofs, we can boldly put our hope and faith in him, though we know it is blasphemous impiety to confide in any other creature.  ‘Ye believe in God’, says he, ‘believe also in me’ (Jn 14:1).  And so Paul (Rom 10:11, and 15:12) interprets two passages of Isaiah, ‘Whoso believeth in him shall not be confounded’ (Isaiah 28:16); and, ‘In that day there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek’ (Isa 11:10).  But why adduce more passages of Scripture on this head, when we so often meet with the expression, ‘He that believeth in me shall have eternal life’?

Again the prayer of faith is addressed to him – prayer, which specially belongs to the divine majesty, if anything so belongs.  For the prophet Joel says, ‘And it shall come to pass, that whosoever shall call on the name of the Lord (Jehovah) shall be delivered’ (Joel 2:32).  And another says, ‘The name of the Lord (Jehovah) is a strong tower; the righteous runneth into it and is safe’ (Prov 18:10).  But the name of Christ is invoked for salvation, and therefore it follows that he is Jehovah.  Moreover, we have an example of invocation in Stephen, when he said, ‘Lord Jesus, receive my spirit’; and thereafter the whole Church, when Ananias says in the same book, ‘Lord, I have heard by many of this man, how much evil he hath done to thy saints at Jerusalem; and here he hath authority from the chief priests to bind all that call on thy name’ (Acts 9:13-14).  And to make it more clearly understood that in Christ the whole fullness of the Godhead dwelt bodily, the Apostle declares that the only doctrine which he professed to the Corinthians, the only doctrine which he taught, was the knowledge of Christ (1 Cor 2:2).  Consider what kind of thing it is, and how great, that the name of the Son alone is preached to us, though God command us to glory only in the knowledge of himself (Jer 9:24).  Who will dare to maintain that he, whom we know forms our only ground of glorying, is a mere creature?  To this we may add, that the salutation prefixed to the Epistles of Paul pray for the same blessings from the Son as from the Father.  By this we are taught, not only that the blessings which our heavenly Father bestows come to us through his intercession, but that by a partnership in power, the Son himself is their author.  This practical knowledge is doubtless surer and more solid than any idle speculation.  For the pious soul has the best view of God, and may be said to handle him, when it feels that it is quickened, enlightened, saved, justified, and sanctified by him.

Calvin, John, Institutes of the Christian Religion, 1962, Volume 1, James Clarke and Co. Ltd., London.