The quotation means that Mr. Birling is a practical, unsentimental businessman, a man with a brutally realistic outlook on life.

This is just the kind of person we'd expect a successful businessman to be. The above quotation is very revealing of Mr. Birling's character, showing him to be a no-nonsense individual always willing to speak his mind.

The context of his comments concerns the engagement of Mr. Birling's daughter Sheila. Birling is delighted with the arrangement. Even though he's a hard-headed businessman who's spent his entire business career taking risks, he has no truck with any kind of negativity or pessimism concerning the prospect of Sheila's getting married.

Birling's optimism also extends to the rumblings of war that are going on in Europe. Contrary to what many people think, Birling is convinced—wrongly, as it turns out—that there will be no war, as no one wants it.

In this particular scene, Birling is shown as a rather pig-headed, opinionated man with exceedingly bad judgment. His wealth and success as a businessman have given him a sense of infallibility, which, in due course, will be undermined by the mysterious Inspector Goole.