The horrific events which unfolded in New York last Tuesday have left global markets in turmoil.
The enormity of the human tragedy that unfolded before our eyes was so awful that it was impossible to get one's head around any notion of financial or economic implications.
But, difficult as it seems, these are issues that must be addressed. The crucial starting point is the US and the impact these events will have on consumer and business confidence there. The US economy has been staggering along at very pedestrian growth rates for more than a year now, and we know it would have been a lot worse but for the US consumer.
Admittedly, consumer sentiment has already been dented by events in the economy and stock markets over the last 18 months, but by nothing like the magnitude which many had feared. Will last week's events further weigh on consumers' propensity to spend? The honest answer is that we don't know. We have no template or past experience on which to judge the impact of such appalling events.
But my strong instinct is that it must. The mindset of the entire US nation has been so traumatised that it is hard to believe it won't have a material impact on spending patterns.
The same must be true of business confidence. This is all the more worrying, given that confidence of the business community in the US had already been severely damaged by the shake-out in the technology sector and the corresponding collapse in many share prices.
As a result, spending and investment plans had already been sharply curtailed, and I have to believe that belts will be further tightened following last week's attacks.
Even before last week, most forecasters expected the US economy to continue to grow at a rather sluggish pace over the balance of this year and no material recovery was anticipated until well into 2002.
At a very minimum those expectations must now be reinforced, but it is impossible at this point to quantify what the magnitude of the impact will be.
This is not good news for Ireland, particularly as it comes at a time when there is mounting evidence that the economy slowed appreciably during the summer months. Volumes of international trade have already contracted, as has output in the manufacturing sector.
At the same time, falling tax receipts suggest that the slowdown has extended to the broader economy.
There are certain areas where the events will have a particular impact on the Irish economy. Firstly, the impact on trade flows. The US is now an important destination for Irish exports, and any slowing in overall demand there will have some impact on such flows.
Secondly, and more importantly, is direct investment by US firms into Ireland.
This was a key driver behind the exceptional growth rates achieved by the Irish economy in the second half of the 1990s. If business confidence weakens then US firms will curtail spending plans in relation to overseas expansion.
Finally, there is the particular impact these attacks will have on the propensity of Americans to travel abroad.
In the immediate aftermath of these atrocities, US citizens will certainly cut back travel plans.
But the impact may have paled by the time the tourism season gets going in earnest next summer, unless, of course, the US engages in retaliatory action that will raise similar concerns again.
But it may not be all bad news. The main hope is that central banks will react by aggressively reducing interest rates, which will help stem any dramatic slowdown. On the basis of recent experience we can be confident that the Fed will do whatever is needed to keep the US economy on track. Whether the ECB manages to extract its head from the sand is another matter.
Robbie Kelleher is head of research at Davy Stockbrokers