'In philosophy where truth seems double-faced there is no man more paradoxical than myself, but in Divinity I love to keep the road. 
A few paragraphs later he introduces his highly original proper-name symbolism, stating -
'yet I perceive the wisest heads stand like Janus in the field of knowledge'. 
in other words, the true intellect respects the wisdom of the past as well as advancing knowledge for future generations.
Browne's subsequent publication, the encyclopaedic endeavour Pseudodoxia Epidemica (1646-72) challenged and refuted many of the superstitions and folk-lore beliefs prevalent in his day in favour of reason, experience and 'occular observation'. This included a rejection of medical cures by means of amulets and minerals, the learned doctor wittily remarks-
'he must have more heads than Janus, that makes out half of those virtues ascribed unto stones and their not only medical, but magical properties, which are to be found in Authors of great name'. 
The Roman god Janus is ingeniously used by Browne as a 'conjoining' symbol which unites his twin philosophical discourses Urn-Burial and The Garden of Cyrus (1658). Structured upon the metaphysical templates of Time (Urn-Burial) and Space (The Garden of Cyrus) and highly polarised in imagery, respective truth and literary style, Browne's twin Discourses remain unique in World literature. In Urn-Burial the gloomy, stoical and funerary half of the literary diptych, the learned physician laments
'We cannot hope to live so long in our names, as some have done in their persons, one face of Janus holds no proportion unto the other'. 
in other words, everyone has either a greater or lesser proportion of their life remaining. No-one can ever know for certain just when they have arrived at the equidistant point of their lives, the past and the future are unequal in all lives.
Janus is also encountered in the esoteric discourse The Garden of Cyrus. With typical subtle humour Browne declares-
'And in their groves of the Sun this was a fit number, by multiplication to denote the days of the year; and might Hieroglyphically speak as much, as the mystical Statua of Janus in the Language of his fingers. And since they were so critical in the number of his horses, the strings of his Harp, and rays about his head, denoting the orbs of heaven, the Seasons and Months of the Year; witty Idolatry would hardly be flat in other appropriations'. 
Ever helpful to his reader, Browne adds an explanatory foot-note- 'Which King Numa set up with his fingers so disposed that they numerically denoted 365'. i.e. Numa reformed the Roman calendar.
A primary source of information about Janus can be found in Ovid's Fasti (Festivals). Over a dozen books by the Roman poet Ovid (43 BCE - 17 CE) including Fasti as well as several editions of his most famous work Metamorphoses are listed as once in the combined libraries of Thomas Browne and his eldest son Edward. The opening page of Ovid's Fasti narrates firstly of how the poet encounters and questions Janus, the poet reminding his reader that there is no equivalent to Janus in the Greek pantheon of gods -
'Yet what god am I to call you, biformed Janus ? / For Greece has no deity like you'.
Janus subsequently informs the poet of his origins and attributes thus-
'The ancients (since I'm a primitive thing) called me Chaos.
Then I, who had been a ball and a faceless hulk,
Got the looks and limbs proper to a god.
Now as a small token of my once confused shape,
My front and back appear identical....
Whenever you see around, sky, ocean, clouds, earth,
They are all closed and opened by my hand.....
Just as your janitor seated by the threshold
Watches the exits and the entrances,
So I the janitor of the celestial court
Observe the East and West together'.
The celestial 'janitor' who has the power to open and to close is defined as the god of mysteries in general by Ovid who recounts one of the few surviving myths known of Janus. Ovid tells of a deceitful nymph called Carna whom many lovers pursued, but all in vain.
'A young man would declare words of love to her,
And her immediate reply would be:
''This place has too much light and the light causes shame.
Lead me to a secluded cave, I'll come''.
He naively goes ahead; she stops in bushes
And lurks, and can never be detected.
Janus had seen her. Clutched by desire at the sight,
He deployed soft words against her hardness.
The nymph, as usual, demands a more remote cave,
Trails at her leader's heels and deserts him.
Fool ! Janus observes what happens behind his back
You fail; he sees your hideout behind him.
You fail, see, I told you: as you hide by that rock,
He grabs you in his arms and works his will.
'For lying with me,' he says, 'take control of the hinge;
Have this prize for your lost virginity'. 
The primary attributes of Janus are hindsight, the ability to learn from past events and foresight, the ability to anticipate future events. These attributes may have contributed in no small measure towards the continuity of Roman civilization on both an individual and collective basis. The Roman Emperor Marcus Aurelius (121 -180 CE) in his stoical Meditations (listed as once in Browne's library) gives Janus-like advice his reader-
'Look closely at the past and its changing Empires, and it is possible to foresee the things to come'. 
'In ancient poetry these souls were signified by the double-headed Janus, because, being supplied like him with eyes in front and behind, they can at the same time see the spiritual things and provide for the material'.
Browne was a pioneering scholar of comparative religion, that is, the study of religious beliefs, their doctrines and symbols, alongside their spread and influence in the world. Assisting him in this study were the six modern languages he was fluent in, as well as Greek, Latin and Hebrew. Although at times misguided in his study, notably by the Jesuit scholar Athanasius Kircher (1602-80) whose books are well-represented in his library and to whom he somewhat slavishly believed, nonetheless his tolerance and broad-mindedness, paved the way for future scholars. As stated earlier, Janus is exclusively a Roman god without Greek equivalent. It was not until the eighteenth century that the British philologist Sir William James (1746-94) detected linguistic similarities between Sanskrit and Latin which indicated that Janus originated from the Indian elephant-headed god Ganesh. Its highly probable that Roman merchants who travelled to India for luxury goods such as saffron introduced and modified the Indian god to the Roman world.
Late in his life Browne wrote, though never published, an advisory for the benefit of his children. Christian Morals is Browne's last known written work. Published posthumously (1716) its an equal testimony to Religio Medici in his adherence to the Christian faith; nevertheless mention of alchemy and astrology along with Hermes Trismegistus can also be found within its pages. The name of Janus occurs no less than four times in Christian Morals, primarily in the guise as a moral figure advising the reader to learn from hindsight and to develop foresight in their life.
Browne firstly links the temple of Janus in ancient Rome whose doors were shut during peace-time and open during times of war to individual temperament. He cautions his reader to - 'keep the Temple of Janus shut by peaceable and quiet tempers' 
Next, he advises that when in doubt one should opt for virtue-
'In bivous theorems and Janus-faced doctrines let virtuous considerations state the determination.' 
The stoic moralist also instructs his grown-up children to-
'Let the mortifying Janus of Covarrubias be thy daily thoughts'' 
adding the explanatory footnote - 'Don Sebastian de Covarrubias writ 3 Centuries of moral emblems in Spanish. In the 88th of the second century he sets down two faces averse, and conjoined Janus-like, the one gallant beautiful face, the other a death's head face, with this motto out of Ovid's Metamorphosis Quid fuerim quid simque vide'. ('See what I was and what I am now').
Lastly, Browne juxtaposes Roman mythology to Biblical scripture in vivid imagery, declaring-
'What is prophetical in one age proves historical in another, and so must hold on unto the last of time; when there will be no room for prediction, when Janus shall lose one face, and the long beard of time shall look like those of David's servants, shorn away upon one side.' 
The Old Testament book of Samuel recounts that-
'Wherefore Hanun took David's servants, and shaved off the one half of their beards, and cut off their garments in the middle, even to their buttocks, and sent them away'. 
The Biblical figure of King David is now believed to have lived circa 1010–970 BCE. Its worthwhile remembering that the King James Bible (1611) with its soaring strophes, rhythmic cadences and striking parallelisms was the predominant influence upon Browne's spirituality. Freshly translated from Hebrew by a host of scholars, the text of the King James Bible was, in all probability, the first book which young Thomas learnt to read as a child, and subsequently a powerful influence upon his literary style as an adult.
Browne's own Janus-like ability to 'foresee' the future is testified in a memoir by the Reverend Whitefoot. The Heigham-based priest was a close friend of Browne's from the newly-qualified physician's arrival to Norwich in 1637 until 1682 when Browne upon his death-bed gave 'expressions of dearness' to his long-time friend. Reverend Whitefoot's memoir includes the character testimony-
'Tho' he were no prophet, nor son of a prophet, yet in that faculty which comes nearest it, he excelled, i.e. the stochastick, wherein he was seldom mistaken, as to future events, as well publick as private; but not apt to discover any presages or superstition'.
Even greater testimony to Browne's ability to prognosticate the future can be found in the miscellaneous tract known as 'A Prophecy concerning the future state of several nations'. Imitative of the opaque verse of Nostradamus, Browne's 'Prophecy' consists of a series of couplet verse 'predictions' several of which on America. In Browne's proper-name symbolism America is invariably equated with the new, exotic and unexplored, a good example occurring in Pseudodoxia Epidemica in which he describes his encyclopaedic endeavours as, 'oft-times fain to wander in the America and untravelled parts of Truth'. At least three 'predictions' in 'A prophecy concerning the future state of several nations' are remarkable -
* 'When Africa shall no more sell out their Blacks/ To make slaves and drudges to the American Tracts'.
* 'When America shall cease to send out its treasure/But employ it at home in American pleasure'.
* 'When the new world shall the old invade/Nor count them their lords but their fellows in trade'.
Browne's 'prophecy' concludes thus-
'Then think strange things are come to light/ Where but few have had a foresight'. 
In conclusion, Thomas Browne's life-long penchant for utilizing Janus as a symbol is illuminated by the psychologist Carl Gustav Jung who considered Janus to be -
'a perfect symbol of the human psyche, as it faces both the past and future. Anything psychic is Janus-faced: it looks both backwards and forwards. Because it is evolving it is also preparing for the future'. 
I've written before about the many ideas shared between Browne and Jung. Not only does one of the earliest recorded usages in modern English of the word 'archetype' occur in Browne's hermetic vision, The Garden of Cyrus but the archetype of 'the wise ruler' itself is sketched through highly original proper-name symbolism. King Cyrus, Moses, Alexander the Great, Julius Caesar, Solon, Scipio, King Cheops, Hermes Trismegistus and Augustus are all cited in the discourse as exemplary of 'the wise ruler' archetype.
Nowadays the phrase 'two-faced' more often than not is used as a pejorative term, however, from his deep study of the Ancient world to his anticipation of 'future discoveries in Botanical Agriculture', there's a good case to be made for Thomas Browne to be lauded as the Janus-faced sage of Norwich. The learned physician-philosopher's assessment of our own increasingly uncertain times was one which was, 'not like to envy those that shall live in the next, much less three or four hundred Years hence, when no Man can comfortably imagine what Face this World will carry'.  What is certain however is that centuries before C.G. Jung, the proto-psychology of Thomas Browne utilized Janus as symbolic of the human psyche. And just like the Roman god Janus, whose name is remembered in the month of January, we too continue to look back to the past and forward to the future in order to define our identity.