Mal Fletcher comments on yesterday's attack on Westminster Bridge.

Terrorists offer no hope for the future, only a blinkered vision of the past and a brutally incoherent understanding of the present.

Ask most people what dominant trait marks out terrorists from the rest of us and many will answer, intolerance. Yet the terrorists' fundamental failure lies deeper than this, in their seeming inability or refusal to acknowledge the human hunger for respect.

Much is said about tolerance these days, yet it is inferior to respect. Tolerance often assumes a downward-looking posture. 'Look at you,' it says, 'with all your strange beliefs and even stranger behaviour. It's a good thing that I'm as tolerant as I am or we'd never co-exist.'

Respect, by contrast, assumes a level stance or even an upward-focused outlook. 'I disagree with you on some things,' it declares. 'At times, we disagree vehemently. Yet I recognise your inherent value as a human being and I acknowledge that there is likely much I can learn from you.'

Through the ages, this has been the fundamental difference between two of the biggest change-agents across civilisations - violent conquerors and servant-minded missionaries.

The former have sought to quench identity and bring change through a strategy of alienation-for-integration. Separate people from all that they hold dear, their thinking goes, and their identity can be re-engineered, their worldview re-programmed.

Throughout history, however, true missionaries - as opposed to opportunistic colonialists - have tried to bring constructive change through persuasive advocacy and by modelling a more beneficial way forward.

They have recognised that a human conscience is sacrosanct; that it may be wooed, persuaded and challenged but it should not be bullied.

When a former-slave-turned-churchman by the name of Patricius left Romanised England to serve the people of Ireland, he encountered there a fierce, warrior-like culture. Change came through violence and the threat thereof. Alpha males wore the shrunken heads of their enemies in their belts as a status symbol.

Within little more than a generation, Patricius and his monks had seen the culture largely transformed, to the point where men wore small scrolls in their belts to signify their newly acquired literacy skills.

Later, during the invasions of Europe by the barbarians, it was the disciples of St Patrick (as we know him) who helped to rescue and preserve the foundational works of western literature.

Ireland's change was not the result of conquest or acts of terror. It was brought about by the promotion of education and trade, on the basis of hope for a better life and basic respect of the other.

Terrorists seek to convert by breeding insecurity, but human beings are inherently wired to seek and feed off hope and to seek and show respect.

Terrorists, acting alone or in groups, may try to sow insecurity. At times they will succeed, in measure. But they will not produce the large-scale change for which they yearn.

Their ultimate failure will not be a result of iron-clad security measures. As our police officials have reminded us again today, there is no such thing as perfect security.

Their plans will be frustrated because hope and respect are more life-affirming than horror and disrespect.