In the tales that European diplomats and officials recount of their political masters' meetings with Vladimir Putin there is a near universal observation about the Russian president and it amounts to this - he lies as easily and unthinkingly as other people breathe.
Mr Putin will look his interlocutors straight in the eye and tell them something that they both know is simply untrue. He will make promises that are broken the following day. He will agree something at a meeting and the following week he will act as if the meeting never took place.
None of this is meant to demonise Mr Putin. He is not mad or messianic. He is not prone to acting without very careful - and usually very astute - calculation. And he is less dangerous than many other potential leaders of the autocratic former superpower.
But since Moscow effectively ended the post-cold war European order with its invasion of Ukraine earlier this year, second-guessing Mr Putin's intentions and motives has become the near-obsession of politicians, diplomats and foreign policy intellectuals in democratic Europe. Officialdom and the think tank world across the continent have done more Kremlin-watching over the past six months than at any time since the Soviet Union ceased to exist.
What Mr Putin wants - and is prepared to do to achieve his ambitions - are now the central issues for Europe's security because if he intends to extend Russia's "sphere of influence" to include EU and NATO members, then there is the possibility of a full-scale war on the continent. It is that serious.
If the limit of his ambition was to guarantee security of the pro-Russian people of eastern Ukraine then there would be reason to hope that the tentative ceasefire agreed on Friday would give the breathing space for a broader political compromise which, in turn, could lead to a durable settlement taking into account the legitimate interests of all actors.
But nobody now believes that the human, civil and political rights of Russian speakers living outside Russia are Mr Putin's only concern. There were, for instance, many less destabilising ways that the rights of Russians in Crimea could have been protected, other than by the annexation of the entire territory. But none of these was either attempted or even explored.
Having used the rights issue as a reason for annexation once, there is good reason to think that it could happen again. And all the more so in Eastern Ukraine. The Russian president's frequent use of the Tzarist-era term Novorossiya (New Russia) to describe the area where fighting has taken place could be a pretext for annexation of whole swathes of Ukraine.
All of this underscores the fact that Russia insists on playing by its own rules and, unlike the rest of Europe, views the use of force against its neighbours as an acceptable tool in the pursuit of its interests. This posture has very deep historical roots that will not change any time soon. As this column has argued before, the evolution of Russian society and politics over centuries differs greatly from the rest of Europe. The result, among many other things, is that the values and worldview of the Russian people and its leaders are very different from most of the rest of Europe.
While the democracies have peace and prosperity as their most cherished goals, Mr Putin has shown time and again that power and prestige are more important to him and, opinion polls suggest, to the Russian people. One of many recent examples of how these differences manifest is his claim that he could "take Kiev in two weeks". It is impossible to imagine any other European leader threateningly bragging about how quickly their forces could capture a neighbour's capital.
But whatever other leaders think of him, they cannot avoid facing the challenge he poses. And in this they have struggled, with Mr Putin attempting, often successfully, to outmanoeuvre them and play them off against each other. Indications are that he is doing exactly that right now.
Many wonder if it was a coincidence that the ceasefire agreed on Friday came just a day before fresh sanctions on Russia were to be agreed by the EU in response to clear evidence that the Russian military had crossed into Ukraine. Some EU members who lean towards Russia or fear the economic effects of retaliatory sanctions are, behind the scenes, calling for the imposition of the sanctions to be postponed. It is just such divisions that Mr Putin seeks to sow.
What does all this mean for Ireland? We are fortunate to be situated in what is the safest corner of our region, far from muscle-flexing dictators in the east and the troublespots of the southern and eastern Mediterranean. But the return of Russia as a source of real insecurity in Europe has consequences for us beyond the economic cost of the counter sanctions Russia has put in place.
For some time, long pre-dating the Ukraine conflict, there have been murmurings from neutral members of the EU that they are losing influence in discussions in relation to foreign policy and security issues as the bloc tries to leverage its clout in the world by taking more common positions.
Recent Russian actions have caused those murmurings to grow louder triggering, among other things, fresh debates among fellow neutrals - Finland and Sweden - about joining Nato.
A number of countries have also announced increased military spending in proportion to the greater threat they face. This could result in a push for a greater security and defence role for the EU - it's worth recalling that in the 1950s the first step towards European integration was the European Defence Community and that the economics-focused community only came about after the French parliament rejected the military union.
It is unlikely that relations with Russia will improve and possible that the EU, in response to events in Ukraine, will become more involved in hard defence issues. It is not impossible that we could then be placed in a position of having to hold an EU treaty referendum which would, in effect, be a choice between staying in the EU or leaving to remain neutral.
Dan O'Brien has previously worked in the foreign service of the European Commission and was Europe editor at the Economist Intelligence Unit from 1998-2010