Should Christians GAMBLE?  And how does this differ from INVESTING?
Let's divide the following into two 'slots':

A.  Should Christians gamble?
B.  Is Sharemarket/Forex/(Whatever!) speculation considered gambling?

The above questions - like asking if a particular stock is worth buying or not(!) - usually involve far more complexity than a simple Yes/No.  At the outset let's be clear that all our decision-making, especially on non-trivial issues, need to be approached within the context of our relationship with God.  Asking if it's 'proper' for the guy (and not the girl) to always settle the bill on a date would be highly irrelevant if the guy and girl do NOT love each other in the first place.  It simply wouldn't be the proper question at all, would it?  Like making plans for a new car when the family is in crisis...

Same thing here.  Before we even start to start, we must be sure that our spirits have already been surrendered to God and that we're not looking at the question in the same manner of heart as we would in filing for tax exemptions.

Now for the first roll of the dice...

A.  Should Christians gamble?

For the sake of a working definition of the term 'gambling', let's tentatively work with the 'culturally accepted' activities falling under that label, e.g. playing cards, roulette, one-armed bandit, black-jack, horse-racing, lottery, etc.  Towards the end of the piece I'll try to address the 'controversial' activities (like stock market and forex speculation, etc.) which some people consider to be gambling but others do not.  But for now, let's just stick with those events which no one would dispute is NOT gambling.

My understanding of Scripture leads me to reply "No, you should not gamble if...":

1.  Other people will have their faith 'shaken' or their perception of Christ jeopardised as a result  of witnessing our activities.  I'd see this as the most important reason to watch ourselves regarding this issue (and any other 'contemporary issue' regarding which Scripture is relatively silent).  Remember always that often the only image of God which others see is His image in us - let's always make sure it shines forth righteousness, peace and joy.  Growing to be more OTHER-centered will surely make us more sensitive of this issue.

2.  We have a deep spiritual problem regarding money which pervades the heart and mind, clearly leading us away from God.  This usually manifests itself in addictiveness, loss of fellowship and an aggravating of relationships due to our gambling/greed habit (just like a Christian with a serious sexual addictiveness should be 'extra careful' even when looking at art works depicting nudity).  Another way to look at it is that if we can't seem to shake off our guilt each time we toss a dice, then I'd suggest that we don't continue.

3.  The amounts at stake are huge to the point of irresponsibility (betting half our bank accounts on is tantamount to insanity, Christian or non-Christian!).  Note too that a high FREQUENCY of such activities will accumulate the figures being risked, and possibly lost.  Plain responsibility to one's family, not to mention the aspect of Christian financial stewardship, is the key here.

It should be clear by now that the issues of the 'morality' of gambling doesn't feature here so much as does a concept like 'relational sensitivity'.  Gambling may lead us to greed, which in turn may lead to sin (need I elaborate on this?), but usually the activity in itself isn't immoral or sinful.  As with most of our decision-making in life, it should be relationships which must be at the core of the process.

I believe that God wants us to always decide with Him, our family and other people in mind. We must be continually sensitive to our loved-ones, friends and neighbours and the effect our actions may have on them, and what they may think about us and our Father in heaven for whom we must be devoted representatives on earth.

And for the next roll of the dice...

B.  What about stock investments/speculation?  Are these considered 'gambling'?

I hope that by now we can understand that the question above no longer matters, because whether or not it falls under the category of ‘gambling’ the above principles STILL hold!  Thus, asking about the right 'definitional category' for stock-market speculation would all but miss the point.  Instead we should ask:

There is no longer any need (let alone benefit) to engage in pointy and lengthy definitions of investment vis-a-vis speculation/gambling, because if we bear in mind these principles, then what we name a particular activity becomes subordinate to the effect of that activity on our hearts and that of others.  Our labelling of opportunities as gambling or investing become merely that: semantics.

So, we would do well to heed the words of Augustine (or was it Luther?) : "Love the Lord with all your heart, and live as you please - in that order."

Note 1:  Relevant Scripture passages for the above would include 1Cor 10:23-33 and Matt 6:19-24.

Note 2:  A very dear relative of mine (the same one who raised the question) pointed out that we can distinguish Investment from Gambling activities by noting the odds of winning or coming out on top.  'Gambling' would involve odds no better than 50-50 whereas 'Investments' are (or should be?) by definition options giving you higher than a 50% chance of winning.  Although I personally found such a distinction insightful (and I do not dispute it), I'd have to note that we'll need to go deeper than simply making sure that our activities meet the required 'criteria' for being labelled 'non-sin' (grin), that is, if it was our walk with God we were originally concerned about.