Economic activity, i.e. positive-sum trades, are what generate economic output (that and direct labour). Investment and consumption demand can both lead to economic activity. AIUI the available evidence is that with the current economy a marginal dollar will produce a greater increase in economic activity in consumption than in investment.
I think you are failing to make a crucial distinction: positive-sum trades do not generate economic activity, they are economic activity. Investment generates future opportunities for such trades.
Economic activity, i.e. positive-sum trades, are what generate economic output (that and direct labour). Investment and consumption demand can both lead to economic activity. AIUI the available evidence is that with the current economy a marginal dollar will produce a greater increase in economic activity in consumption than in investment.
I think you are failing to make a crucial distinction: positive-sum trades do not generate economic activity, they are economic activity. Investment generates future opportunities for such trades.