First, it can be due to people valuing the item more, or secondly, it can be due to people valuing the money less. Conditions of supply and demand can cause price adjustments of particular goods or commodities. But when the prices of most goods and services are rising simultaneously, that invariably reflects a debasement of the currency in terms of which the prices are stated. Sellers demand more money because each unit of money is worth less than it was before. So to summarize, inflation is a rise in the general level of prices of goods and services, and its cause is the debasement of the official currency.
Few economists seem willing to acknowledge official debasement as the root cause of inflation.
Fewer still offer any effective remedy. Most orthodox proposals seek only to limit the rate of debasement, not to end it. It is not the amount of money in circulation, per se, which causes inflation, but the basis upon which the money is issued. Money which is improperly issued can be viewed as counterfeit, albeit legal counterfeit. It is counterfeit, not because its issuance is unauthorized, but because its issuance violates sound principles of money and banking.